671.705 
 
 M564X 
 
 DEPOSITORY 
 
 Illinois Environmental 
 
 1 1994 
 
 Protection 
 
 AT iJRBANA-CHAMPAIGN 
 
 OFFICE OF POLLUTION PREVENTION 
 
 May 1994 
 
 Q 
 
 Printed on Recycled Paper 
 
UNIVERSITY OF 
 ILLINOIS LIBRARY 
 AT URBANA-CHAMT'AIGN 
 bookstacks 
 
Outline for lEPA Workshop on the Metal Finishing Industry 
 
 
 I. Introduction to the Metal Finishing Industry 
 
 A brief history of the metal finishing Industry and the evolution of metal finishing 
 processes to their modern form. 
 
 II. Metal Finishing Process Overview 
 
 Basic Flow diagrams illustrating the flow of raw materials, products, and wastes. 
 Processing sequence information for various metallic substrates. 
 
 III. Metal Finishing Process Details 
 
 Details of various metal finishing processes, including operating principles, by¬ 
 products, and wastes generated. 
 
 IV. Recycling Methods Used in the Metal Finishing Industry 
 
 Information on the types of recycling methods available for use in the metal 
 finishing industry. 
 
 V. Pollution Prevention Methods in the Metal Finishing Industry 
 
 Process modifications, pollution prevention planning, and substitution methods 
 available for metal finishers. 
 
 VI. Statutory and Regulatory Obstacles to Pollution Prevention 
 
 Regulations and other requirements that can act as barriers to adoption of pollutio 
 prevention by the metal finishing industry. 
 

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Table of Contents 
 
 I. Introduction to the Metal Finishing Industry 
 
 Topic Page Number 
 
 Time Line 2 
 
 Direct Dischargers 3 
 
 Table 1, auxiliary processes regulated under metal finishing 5 
 
 Common Metal Finishing Operations 7 
 
 Anodizing 9 
 
 Phosphating 9 
 
 Conversion Coating 10 
 
 Burnishing 10 
 
 Electropolishing 10 
 
 Chemical Milling 11 
 
 Electropainting 11 
 
 Vacuum Metallizing 11 
 
 Mechanical Plating 11 
 
 Spray Painting 12 
 
 Powder Coating 12 
 
 f 
 
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Part I, Introduction To The Metal Finishing Industry 
 
 METAL FINISHING 
 
 * Enhance the surface of metal 
 
 * Application of metallic coating 
 
 * Protection from corrosion 
 
 * Enhanced wear properties 
 
 * Enhanced appearance 
 
 "Metal Finishing" is a generic term applied to a variety of processes for the purpose of 
 enhancing one or more properties of the surface of a metal. It is also applied to a number 
 of processes that involve the application of a metallic coating to a non-metallic surface 
 such as plastic, ceramic, epoxy, and even baby shoes. 
 
 The art of creating an altered surface on a metallic substrate dates back to several 
 centuries before Christ. Methods of metal finishing such as polishing, grinding, and 
 painting were performed in the same era, along with non metal finishing processes such 
 as heat treating and tempering of metals. 
 
 The modern metal finishing era, however, began with the invention of the galvanic cell in 
 the early 1800's. By the middle of the 19th century, silver, gold, copper, and brass 
 plating were commercially performed. In addition to electroplating, numerous competitive 
 methods of altering the surface of metals and non-conductors have been added to the 
 common definition of metal finishing since the 19th century. 
 
 Early metal finishing processes were focused on decorative endeavors such as jewelry 
 and decorative items such as lamps and hardware. However, some massive parts were 
 manufactured utilizing an electroplating method called "electro-forming", including the 
 street lamp standards for the streets of Paris. 
 
 The metal finishing industry received a big boost from the advent of the industrial age, 
 and the development of electricity generators in the late 1800s. Metal machine 
 components, hardware, and automotive parts required protection from corrosion 
 enhanced wear properties, and enhanced appearance. 
 
 World Wars I and II and the aircraft industry further developed and refined the industry by 
 adding such processes as anodizing, conversion coating, chromium plating, bronze alloy 
 plating, nickel plating, chemical milling and phosphating, along with numerous other 
 plating processes. Plating equipment evolved from manually operated wooden process 
 tanks to automated equipment, capable of processing thousands of pounds per hour of 
 parts. 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 1 
 
METAL FINISHING TIME LINE 
 
 <-0 
 
 1800 
 
 1850 
 
 1917—1945 
 
 1945*’—> 
 
 1969 
 
 1972 
 
 1977 
 
 1 Galvanic 
 
 1 
 
 Anodizing 
 
 Electro-paint 
 
 1 
 
 Water 
 
 I 
 
 1 
 
 Cell 
 
 1 
 
 Conv* Coating 
 
 Electroless Pltg 
 
 1 
 
 Pollution 
 
 I 
 
 Polishing 
 
 
 Silver 
 
 Chromium PItg 
 
 Eiectropolishing 
 
 1 
 
 Control Act 
 
 I 
 
 Grinding 
 
 
 Gold 
 
 Bronze Alloy 
 
 Vacuum Metalizing 
 
 1 
 
 
 Clean 
 
 Painting 
 
 
 Copper 
 
 Nickel Pltg 
 
 Mech. Pltg 
 
 1 
 
 
 Water 
 
 Heat treat 
 
 
 Brass 
 
 Chem. Milling 
 
 Electrostatic paint 
 
 1 
 
 
 Act 
 
 Tempering 
 
 
 Plating 
 
 Phosphating 
 
 Electrolytic paint 
 
 1 
 
 
 
 
 
 
 Other 
 
 Powder coating 
 
 1 
 
 
 
 MSD 
 
 The modern era of metal finishing arrived following World War 11. Processes such as 
 electro-painting, electroless plating, electropolishing, vacuum metallizing, mechanical 
 plating, electrostatic painting. Electrolytic painting (E-coat), and powder coating. 
 
 The peak of the metal finishing era is believed to have occurred during the 1950-1960 
 decade, with approximately 6000 job shops providing plating services and an unknown 
 number of large manufacturers (such as Sunbeam, General Electric, and Westinghouse) 
 employing metal finishing facilities as part of their manufacturing processes. 
 
 Until 1972, the metal finishing Industry was environmentally unregulated (except for 
 selected areas such as Chicago, where a local ordinance by the Metropolitan Sanitary 
 District was passed in 1969) and discharges of concentrated chemicals from metal 
 finishing processes to sewer systems and surface waters was common. In 1972, 
 Congress gave the Environmental Protection Agency (USEPA) the authority to create 
 regulations for industrial dischargers to the surface waters of the USA, under the Water 
 Pollution Control Act (Public Law 92-500). In 1977, Congress gave EPA additional 
 powers to regulate discharges to sewers under the "Clean Water Act (Public Law 95- 
 217). Under this mandate from Congress, EPA developed a system of "categorizing" all 
 industries that discharged pollutants to the surface Waters and sewers of the USA. EPA 
 then passed regulations limiting the concentrations and amounts of pollutants that could 
 be in the discharges of process water from those categorical industries. EPA also studied 
 and provided technical information on what technologies could be employed to comply 
 with their regulations. 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 2 
 
DIRECT DISCHARGERS: 
 
 • NPDES PERMIT 
 
 • TOXIC POLLUTANTS 
 
 • CONVENTIONAL POLLUTANTS 
 
 • TECHNOLOGY: 
 
 Precipitation 
 Clarification 
 CN-Destruct 
 Cr-reduction 
 Oil Removal 
 
 Precious Metals Recovery 
 
 EPA realized that the most serious threat to the environment arose from facilities that 
 discharged directly into the rivers (navigable waters such as lakes, bays, rivers, creeks, 
 and most all other surface waters down to very small rivulets). They, therefore, first 
 passed regulations on those discharges and thereby created the National Pollutant 
 Discharge Elimination System (NPDES). Under this system, an NPDES permit is issued to 
 each direct discharger. This permit specifies the maximum concentration of each 
 pollutant in addition to such things as BOD (Biochemical Oxygen Demand), TDS ( Total 
 Dissolved Solids), FOG (Fats, Oils, and Greases), and numerous other "conventional" 
 pollutants (pollutants that are not toxic and are normally assimilated by the receiving 
 stream, but can significantly affect the quality of the receiving stream). 
 
 NPDES discharge limits are based on BAT/BPT - that is the best practicable control 
 technology presently available. The technology used for compliance purposes includes 
 "precipitation of metals and clarification plus cyanide destruction, reduction of hexavalent 
 chromium to trivalent, oily waste separation, precious metals recovery, and total toxic 
 organics (TTO ) control". Note that most discharge regulations are concentration based 
 (usually measured in mg/L). Some specific regulations allow the option of mass based 
 standards (measured in mg/Kg of parts processed). 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 3 
 
40CFR parts 400-424 
 
 40CFR part 413 Electroplating 
 Point Source Category 
 
 40 CFR part 433 Metal Finishing 
 Point Source Category 
 
 Subparts A: Common Metals 
 B: Precious Metals 
 C: Specialty Metals 
 D: Anodizing 
 E; Coatings 
 
 F: Chemical Etching/ Milling 
 G: Electroless Plating 
 H: Printed Circuit Board 
 
 There are now discharge regulations covering every source of metal finishing wastewat^ 
 These can be found in the "Code of Federal Regulations" (40CFR) parts 400 to 424 an9 
 parts 425 to 629. A job shop electroplating company that existed prior to August 8, 
 1981, (a job shop is one that processes at least 51 % of parts that are owned by others), 
 is regulated per part 41 3 of 40CFR. Note that part 413 is divided into Subparts A 
 through H and each subpart may have different regulations. If the company has a single 
 discharge but performs multiple processes under various subparts, then the most 
 stringent of the differing regulations apply. A job shop electroplating Company that came 
 into existence after August 8, 1981 is considered a new source metal finisher and is 
 regulated under section 433 of 40CFR. 
 
 The "metal finishing industry" covered so far, has been a "generic", commonly used 
 reference. However, EPA created a legal definition of what activities constitute metal 
 finishing under the Clean Water Act of 1977 (published Feb. 28, 1981). A company falls 
 into the metal finishing category under the following circumstances: 
 
 If the company processes fewer than 50% (based on surface area) of parts that are 
 owned by others and performs any one of the following processes: Electroplating, 
 Electroless Plating, Anodizing, Coating (chromating, phosphating, coloring), chemical 
 etching & milling or Printed Circuit Board Manufacture, the metal finishing regulations 
 apply to the wastewater discharges from these operations and from any of the 45 
 operations listed in Table 1. 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 4 
 
TABLE 1 
 
 AUXILLIARY PROCESSES REGULATED UNDER METAL FINISHING IF ONE OR MORE OF 
 THE SIX PRIMARY METAL FINISHING OPERATIONS IS PERFORMED. 
 
 Cleaning 
 Machining 
 Grinding 
 Polishing 
 Tumbling 
 Burnishing 
 Impact Deformation 
 Pressure Deformation 
 Shearing 
 Heat Treating 
 Thermal Cutting 
 Welding 
 Brazing 
 Soldering 
 Flame Spraying 
 Sand Blasting 
 
 Other Abrasive Jet Machining 
 Electric Discharge Machining 
 Electrochemical Machining 
 Electron Beam Machining 
 Laser Beam Machining 
 Plasma Arc Machining 
 Ultrasonic Machining 
 Sintering 
 Laminating 
 Hot Dip Coating 
 Sputtering 
 Vapor Plating 
 Thermal Infusion 
 Salt Bath Descaling 
 Solvent Degreasing 
 Paint Stripping 
 Painting 
 
 Electrostatic Painting 
 Electropainting 
 Vacuum Metallizing 
 Assembly 
 Calibration 
 Testing 
 
 Mechanical Plating 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 5 
 
Job shop electroplating companies formed after August 8, 1981 and existing job shops 
 that re-locate or massively alter their existing shops, are also categorized as "metal 
 finishers" for purposes or regulation under the Clean Water Act. 
 
 For the balance of this introduction, we shall assume the "generic" definition of metal 
 finishing. 
 
 Following regulation under the Clean Water Act, the industry was deluged by regulations 
 under numerous other "Acts", including RCRA (Resource Conservation and Recovery 
 Act), Clean Air Act, SARA (Superfund Amendments and Reauthorization Act), CERCLA 
 (Comprehensive Environmental Response, Compensation, and Liability Act), EPCRA 
 (Emergency Planning and Community Right to Know Act), and OSHA (Occupational 
 Safety and Health Act). 
 
 With few exceptions, each of these regulations seriously impacted the metal finishing 
 industry and caused it to "evolve" in response. 
 
 CLEAN WATER ACT - Pretreatment systems for removal prior to discharge 
 RCRA - Treat & dispose of wastes in environmentally sound manner 
 CERCLA/SARA - Cautious waste disposal - where & whom 
 EPCRA - Review & Reduce hazardous chemicals 
 OSHA - Protect workers from chemical exposures 
 
 The Clean Water Act caused the industry to install and operate pretreatment systems for 
 the removal of heavy metals and other toxins such as cyanide, prior to discharge. 
 
 Because these pretreatment systems were sized and priced based on volume, the industry 
 investigated and employed water conservation methods such as drag-out rinsing and 
 counterflow rinsing. 
 
 RCRA required the industry to treat and dispose of wastes generated from metal finishing 
 operations and pretreatment systems in an environmentally sound manner. The industry 
 responded by developing alternate processes that generated less waste or waste that was 
 less toxic or non-hazardous. 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 6 
 
CERCLA/SARA caused the industry to become much more cautious about where and 
 whom to send there wastes for disposal, 
 
 EPCRA caused the industry to review and reduce the quantities of hazardous chemicals 
 on hand at any given time, reducing potential danger to their neighbors. 
 
 OSHA regulations have caused the industry to change to less toxic processes and to 
 ventilate their processes in order to protect their workers from chemical exposures. 
 
 Common Metal Finishing Operations 
 
 Today, in addition to between 12,000 and 30,000 captive metal finishing facilities, there 
 are approximately 3,000 job shop electroplating companies. They are considered to be a 
 "service" industry, in that they take parts manufactured by others, apply a metal finishing 
 process or processes to those parts, and then return them to their client. 
 
 Of the 45 processes in Table 1, the following are the most commonly applied metal 
 finishing operations: 
 
 COMMON METAL FINISHING OPERATIONS: 
 
 Electroplating 
 Electroless Plating 
 Anodizing 
 Phosphating 
 Conversion Coating 
 Burnishing 
 Electropolishing 
 Chemical Milling/Etching 
 Electropainting 
 Vacuum Metallizing 
 Mechanical Plating 
 Spray Painting 
 Powder Coating 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 7 
 

 Chemical 
 
 Solution 
 
 DC 
 
 Current 
 
 Reducing 
 
 Agent 
 
 Cost 
 
 Complex 
 
 Uniform 
 
 Coverage 
 
 Electroplating 
 
 X 
 
 X 
 
 
 Low 
 
 No 
 
 Electroless Plating 
 
 X 
 
 
 X 
 
 High 
 
 Yes 
 
 Electroplating is the most commonly applied metal finishing process. It utilizes a 
 combination of a chemical solution formulated to contain metal ions or complexed metal 
 ions plus a DC electric current to convert the metal ions in solution to solid metal atoms 
 on the surface of the substrate that the DC current is applied to. Electroplating offers the 
 advantages of being inexpensive, requiring relatively inexpensive equipment, 
 comparatively easy and safe to do, and easy to do in bulk quantity. Plated metal coatings 
 can be used for a variety of purposes, including corrosion resistance, appearance, m 
 solderability, electrical resistance, electrical conductivity, vibratory bonding, abrasion 
 resistance, electro-forming of a product, and as a matrix to hold abrasives such as 
 diamonds and carbides in cutting tools. By far, the widest variety of metal surface 
 properties can be obtained through electroplating processes. 
 
 Electroless Plating utilizes a chemical solution containing metallic ions, but no DC current 
 is applied. The "electrons" required for reducing metal ions to metal atoms are instead 
 supplied by another chemical ingredient, called a "reducing agent". Electroless plating is 
 very expensive, more dangerous to perform, and difficult to do in bulk quantity. 
 
 Equipment costs are similar. Electroless plating offers the advantage of providing very 
 uniform coverage over complex shapes, while electroplating can not cover complex 
 shapes uniformly, without use of labor consuming shields and auxiliary anodes. 
 
 Electroless plating processes can also provide coatings with unique properties such as 
 magnetism, corrosion resistance and abrasion resistance. Electroless plating processes are 
 commonly employed in the manufacture of electronic components and printed circuit 
 boards (properly termed printed wiring boards). 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 8 
 
CONVERSION COATINGS 
 
 Anodizing 
 
 * Applied to Al and Mg 
 
 * Chemical Solution (no metal ions), DC current ( + ) 
 
 * Converts surface to an oxide, dissolved 
 
 Anodizing is a process most commonly applied to aluminum and magnesium. The process 
 utilizes a chemical solution and DC current to convert the surface of the metal parts to an 
 oxide, commonly called an anodized coating. The process differs from electroplating in 
 that the process solution does not contain metal ions and the coating is not applied to the 
 surface. The surface is actually simultaneously converted to the oxide and dissolved by 
 the chemical solution, creating billions of tiny pores in the coating, which allow the 
 coating to be colorized using dyes and other specialized techniques. During anodizing, the 
 aluminum or magnesium parts have a positive ( + ) DC charge applied, while in 
 electroplating, the parts are negatively (-) charged. 
 
 CONVERSION COATINGS 
 
 Phosphating 
 
 * Converts surface into crystalline phosphate coating 
 
 * 3 Categories: Iron - Spray, prior to painting 
 
 Zinc - Steel, prior to oil 
 
 Manganese - Thick, abrasion resistant 
 
 Phosphating is another "conversion" process, that utilizes an acidic solution containing 
 phosphoric acid and other ingredients to convert the surface of the steel parts into 
 crystalline phosphate coatings. There are three major categories of phosphates, iron, zinc, 
 and manganese. Iron phosphates are most commonly applied in spray operations prior to 
 painting, in equipment typically termed a phosphating line. Zinc phosphate can also be 
 applied prior to painting, but is commonly applied to steel parts (especially fasteners such 
 as machine screws and bolts) prior to application of a corrosion inhibiting oil. The 
 phosphate crystals act as a holding mesh for the oil. Manganese phosphates are very 
 thick, abrasion resistant coatings applied to specialized parts in the aerospace industry 
 and on hardware subjected to an abrasive environment. 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 9 
 
Other Conversion Coatings 
 
 * Black Oxide - Sodium Hydroxide, high temp. 
 
 * Chromating - Chromates & other chemicals, thin film 
 
 * Coloring - Chemicals convert surface to desired color 
 
 Conversion Coating is a generic term for any process that converts the surface of a part 
 to a coating. We have just covered two conversion coatings that are somewhat 
 specialized (anodizing and phosphating), but there are numerous other types of conversion 
 coatings: 
 
 Black Oxide: An immersion process in which metal parts are immersed in a molten 
 solution of sodium hydroxide at high temperature (275 °F) to form a black iron oxide. 
 
 Chromating: An immersion process in which metal parts are immersed in a solution 
 containing chromates and other chemicals for the purpose of converting the surface to a 
 thin film that enhances the corrosion resistance and paint adhesion of the surface. 
 
 Coloring: An immersion process that utilizes chemicals to convert the surface of a metall^ 
 part to a coating that has a desired color. This process is commonly employed by 
 decorative lamp, furniture and hardware manufacturers. 
 
 Burnishing: Water solution with abrasive - vibrated or tumbled 
 
 Electropolishing: Chemical Solution & DC current - mirror smooth 
 surface 
 
 Chemical Milling/Etching: Chemical solution dissolves unmasked area 
 
 Burnishing is a process that utilizes a water solution of soaps and other ingredients along 
 with abrasive media to remove sharp edges and metal slivers from stampings and 
 machined/drilled parts. The parts are vibrated or tumbled with this mixture until the 
 desired finish is obtained. 
 
 Electropolishing utilized chemical solutions and DC current to dissolve off a thin film of 
 metal from a surface in such manner that more metal is removed from the peaks of 
 rough surfaces than from the valleys. The resulting surface can be mirror smooth. The 
 process is most commonly applied to stainless steel components, especially in the food 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 10 
 
service and medical industries, for appearance and because an electropolished surface 
 inhibits bacterial growth. 
 
 Chemical Milling/Etching are processes commonly employed in the aerospace industry and 
 in the manufacture of printed wiring boards. The metal parts are masked with a chemical 
 resistive coating at areas that are not to be etched/milled, and are then immersed in a 
 chemical solution that dissolves the unmasked area at a uniform rate, until the desired 
 amount of metal is removed. 
 
 Electropainting: DC current and specialized paint 
 Vacuum Metallizing: Vaporized metal ions, vacuum chamber 
 Mechanical Plating: Tumbling of solution, metallic powder & glass beads 
 Spray Painting: Solvent or water based, possible charge 
 Powder Coating: High temp, eliminates solvents 
 
 Electropainting utilizes DC current and a specialized paint that becomes adherent to 
 immersed metal parts, when the current is applied. The combination of current and paint 
 allows for more uniform and complete coating of complexed shaped parts. The process is 
 commonly performed by the automotive industry on car body panels and on hardware. 
 
 Vacuum Metallizing is a process that utilized vaporized metal ions in a vacuum chamber 
 that "condense" onto the parts held within the chamber and thus metallize the parts 
 (along with everything else inside the chamber). The process is commonly employed to 
 apply thin metallic films on plastic parts such as toys. Variations of the process are also 
 currently in use to apply thick coatings of aluminum, cadmium, titanium nitride and 
 numerous other coatings on industrial parts, inexpensive jewelry, and aircraft 
 components. The process is almost pollution free, but the equipment is very expensive 
 and limited in productivity. 
 
 Mechanical Plating utilizes water based solutions containing various patented ingredients, 
 plus metallic powder and glass beads. The solution and parts to be coated are tumbled in 
 large rotary tumblers. As the beads and parts impact with each other, the metallic powder 
 is "hammered" into the surface of the parts, creating a coating of the metal powder. The 
 process avoids the use of more hazardous chemicals as in electroplating and does not 
 cause hydrogen embrittling effects on high strength steel, but is limited in appearance and 
 the types/combinations of coatings that can be applied. 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 11 
 
Spray Painting is applied to numerous consumer products utilizing a painting line that may 
 include a phosphating operation prior to painting. The parts are sprayed with various 
 paints that may contain solvents or may be water based. Spray painting may be 
 accomplished with the use of an electrostatic charge applied to the parts in order to 
 attract the paint to recessed areas and created more efficient use of the paint. 
 
 Powder Coating utilized specialized powders that melt onto the parts when heated to a 
 high temperature, thereby creating the "painted" coating. Use of powder eliminates the 
 solvents used in conventional spray painting operations and can created very thick, highly 
 corrosion resistant coatings. Parts must be able to withstand the high temperatures of the 
 baking of the powder (325 °F or more), however. 
 
 METAL FINISHING PROCESSES 
 
 * Part Preparation: Creates rinsewater and spent chemicals 
 
 * The Process: Generates wastes, spent solutions, by-products 
 
 * After processing: Additional chemical operations, stripping, rejects 
 
 * Equipment: Scrubbing, ventilation, filtration 
 
 # 
 
 A modern metal finishing facility may utilize one or more of the above processes to 
 conduct their business. Each process will require the parts to be prepared prior to the 
 application of the process. Such preparation usually utilizes cleaning and pickling 
 chemicals and rinses, creating rinsewater and spent chemicals. The process itself will 
 normally generate wastes and spent solutions or by-products. After processing, there may 
 be additional chemical operations and there also may be stripping operations to handle 
 rejects. The equipment used to process the parts may require ventilation and scrubbing of 
 exhaust air, resulting in additional waste generation from the scrubbing equipment and 
 from maintenance of the ventilation equipment. The process solutions may require 
 filtration equipment to remove particulates that can contaminate the processed surface. 
 The filtration equipment can also generate waste. 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 12 
 
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Table of Contents 
 
 II. Metal Finishing Process Overview 
 
 Tonic 
 
 Paae Number 
 
 Case Study; Decorative Lamp Manufacturer 
 
 1 
 
 Manufacturer of Plated Steel Hardware 
 
 3 
 
 Printed Wiring Board Manufacturer 
 
 4 
 
 Small Job Shop 
 
 6 
 
 Keys to successful electroplating 
 
 6 
 
 Processing Sequences; Leaded brass 
 
 7 
 
 Zinc die castings 
 
 7 
 
 Case hardened steel/high carbon steel 
 
 8 
 
 Aluminum/Magnesium 
 
 8 
 
 400 series stainless 
 
 9 
 
 300 series stainless 
 
 9 
 
 Beryllium/Tellurium copper alloys 
 
 9 
 
 Bronzes 
 
 9 
 
 Titanium 
 
 9 
 
 Vapor Degreasing 
 
 10 
 
 Pickling/Descaling 
 
 11 
 
 Soak cleaning 
 
 11 
 
 Pre-plating operations 
 
 12 
 
 Cleaning 
 
 13 
 
 Acid Dip/Pickling 
 
 14 
 
 Special Dips 
 
 15 
 
 Strikes 
 
 15 
 
 The plating step 
 
 16 
 
 Post plate processing 
 
 16 
 

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PART II, Metal Finishing Process Overview 
 
 METAL FINISHING FACILITIES 
 
 * Varying unit operations 
 
 * Variety of raw materials, chemicals used 
 
 * Variety of wastes generated 
 
 A metal finishing facility will consist of numerous unit operations, each designed to 
 modify the surface or shape of a substrate in sequential order, up to the final process 
 prior to packaging. Depending on whether the facility is a wholly owned department of a 
 larger manufacturing company, or if it is a job shop working on parts owned by others, 
 each facility will have a varying number of these unit operations. Since there are many 
 ways to accomplish the same task, each facility may also employ different technologies 
 in their unit operations. The result is a wide variety of operations, chemicals, and wastes 
 generated. The following are simplified examples: 
 
 Metal Finishing Facilities: Case Studies 
 
 Example 1, Company Manufacturing Decorative Lamps. 
 
 OPERATION 
 
 RAW MATERIALS 
 
 WASTES 
 
 Casting 
 
 Solid Metal Alloy 
 
 Clean-Up Fluids 
 
 De-flashing 
 
 NONE 
 
 Metal Cuttings 
 
 Grinding 
 
 Grinding Wheels 
 Castings 
 
 Metal Fines 
 
 Polishing 
 
 Polishing Wheels 
 Castings 
 
 Buffing Materials 
 
 Exhaust Dust 
 
 Vapor Degreasing 
 
 Chlorinated Solvent 
 
 Spent Solvent/Oil 
 
 Soak Cleaning 
 
 Alkaline Aqueous Cleaner 
 Water 
 
 Spent Cleaner 
 Oil/Grease 
 Solid Sludge 
 Waste Rinsewater 
 
 Electrocleaning 
 
 Alkaline Aqueous Cleaner 
 Water 
 
 Spent Cleaner 
 Oil/Grease 
 Solid Sludge 
 Waste Rinsewater 
 
 © 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 1 
 
Example 1, continued 
 
 OPERATION 
 
 RAW MATERIALS 
 
 WASTES 
 
 Acid Dip 
 
 Sulfuric Acid 
 
 Spent Acid 
 
 
 Water 
 
 Waste Rinsewater 
 
 Copper Strike 
 
 Copper Cyanide 
 Sodium Cyanide 
 Sodium Carbonate 
 
 Waste Rinsewater 
 Filter Residuals 
 Cyanide/Carbonate Solids 
 
 Nickel Plate 
 
 Nickel Sulfate 
 
 Nickel Chloride 
 
 Boric Acid 
 
 Organic Additives 
 
 Waste Rinsewater 
 Filtration Residuals 
 Purification Residuals 
 
 Brass Plate 
 
 Copper Cyanide 
 
 Zinc Cyanide 
 
 Sodium Cyanide 
 Organic Additives 
 
 Waste Rinsewater 
 Filter Residuals 
 Cyanide/Carbonate Solids 
 
 Stain 
 
 Various Staining Chemicals Spent Stain Solution 
 Such As Ammonium Polysulfide 
 
 Buff 
 
 Buffing Wheels 
 Buffing Tallows 
 
 Buff Dust 
 
 Vapor Degreasing 
 
 Chlorinated Solvent 
 
 Spent Solvent/Oil 
 
 Lacquer 
 
 Lacquer 
 
 Thinning Solvents 
 
 Lacquer Residuals 
 Spray Booth Waste 
 
 Stripping of Rejects 
 
 Alkaline Stripping Chemicals 
 
 Spent Stripper 
 
 /?^ AU^. 
 
 
Example 2, Manufacturer of Plated Steel Hardware 
 
 OPERATION 
 
 RAW MATERIALS WASTES 
 
 Machine, Forge, Broach 
 Raw Steel 
 
 Vibratory Finish 
 
 Soak Cleaning 
 
 Electrocleaning 
 
 Acid Dip 
 
 Zinc Plate 
 
 Chromate 
 
 Cutting Fluids 
 Steel Rod/Sheet 
 
 Water 
 
 Soap 
 
 Abrasive Media 
 
 Alkaline Aqueous Cleaner 
 Water 
 
 Alkaline Aqueous Cleaner 
 Water 
 
 Sulfuric Acid 
 Water 
 
 Zinc Cyanide 
 Sodium Cyanide 
 Sodium Carbonate 
 
 Waste Cutting Fluids 
 Metal Fines 
 
 Spent Vibratory Solution 
 
 Spent Cleaner 
 Oil/Grease 
 Solid Sludge 
 Waste Rinsewater 
 
 Spent Cleaner 
 Oil/Grease 
 Solid Sludge 
 Waste Rinsewater 
 
 Spent Acid 
 Waste Rinsewater 
 
 Cyanide/Carbonate Sludge 
 Waste Rinsewater 
 Sludge/Solids 
 
 Various Chromating Spent Chromate Solution 
 Chemicals, Most Contain Waste Rinsewater 
 Hexavalent Chromium Compounds 
 
 © 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 3 
 
Example 3, Printed Wiring Board Manufacturer 
 
 OPERATION RAW MATERIALS WASTES 
 
 Clean Laminate Cooper Laminated Epoxy Sheet Spent Cleaner 
 
 Cleaner 
 
 Water 
 
 Drill registration Holes Copper Laminated Epoxy Sheet 
 Apply Photoresist/Expose Photo-resist 
 
 Copper/Epoxy 
 
 Drillings 
 
 Plastic film 
 
 Etch 
 
 Copper Etching Solution 
 (Typically Ammonium Persulfate) 
 
 Waste Etchant 
 Rinsewater 
 
 Strip Photoresist 
 
 Alkaline Stripper 
 Water 
 
 Spent Stripper 
 And Rinsewater 
 
 Adhesion Promotion Chromium-bearing rinses Spent solution 
 
 (for multi-layer boards) (Alternates: copper oxide solution and Rinsewater 
 
 or zinc or brass plating) 
 
 Lamination 
 
 None 
 
 None 
 
 Drill holes 
 
 None 
 
 Copper/Epoxy 
 
 
 Drillings 
 
 Etchback 
 
 Concentrated Acid or 
 Alkaline/Permanganate 
 (Unless plasma is used) 
 
 Spent Etchback 
 Solution 
 
 (Unless plasma is used) 
 
 Electroless Copper Plate Copper Sulfate 
 
 Fomaldehyde 
 Complexing Agents 
 Water 
 
 Spent Plating Solution 
 Rinse Water 
 
 Copper Plate 
 
 Copper Sulfate Rinsewater 
 
 Water Excess Plating Solution 
 
 Sulfuric Acid Contaminated Filter Media 
 
 Apply Photoresist/Expose Organic Maskant Material Plastic Film 
 
 Overplate (tin-lead) 
 
 Lead Fluoborate 
 Tin Fluoborate 
 Fluoboric Acid 
 Water 
 
 Rinsewater 
 Contaminated Carbon 
 (from periodic treatment) 
 
 © 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 4 
 
Example 3 continued 
 
 OPERATION 
 
 RAW MATERIALS WASTES 
 
 Strip Photoresist 
 Etch 
 
 Alkaline Stripper 
 Water 
 
 Copper Etching Solution 
 (Typically Ammonium Persulfate) 
 
 Spent Stripper 
 And Rinsewater 
 Waste Etchant 
 Rinsewater 
 
 Solder Reflow 
 
 None 
 
 None 
 
 Selective Solder Strip 
 
 Selective Nickel Plate 
 
 Selective Gold Plate 
 
 Final Drilling/machining 
 of groves/slots 
 
 Acid Stripping Solution 
 Water 
 
 Nickel Sulfate 
 Nickel Chloride 
 Boric Acid 
 Organic Additives 
 Water 
 
 Potassium Gold Cyanide 
 Additive Salts 
 Water 
 
 None 
 
 Spent Stripper 
 
 Rinsewater 
 Filtration Media 
 Contaminated carbon 
 
 Contaminated Ion 
 Exchange Resin 
 (sent for reclaim) 
 
 Copper/Epoxy Fines 
 (May also contain tin and lead) 
 
 Note: there are many variations on the manufacturing process for printed wiring boards, 
 only the basic steps are covered. Some operations may skip one or more of these steps 
 or use alternate means. 
 
 © 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 5 
 
Example 4, Small Job Shop Electroplater 
 
 OPERATION 
 
 RAW MATERIALS 
 
 WASTES 
 
 Soak Cleaning 
 
 Alkaline Aqueous Cleaner 
 Water 
 
 Spent Cleaner 
 Oil/Grease 
 
 Solid Sludge 
 
 Waste Rinsewater 
 
 Electroclean 
 
 Alkaline Aqueous Cleaner 
 Water 
 
 Spent Cleaner 
 Oil/Grease 
 
 Solid Sludge 
 
 Waste Rinsewater 
 
 Acid Dip 
 
 Sulfuric Acid 
 
 Water 
 
 Spent Acid 
 
 Waste Rinsewater 
 
 Zinc Plate 
 
 Zinc Cyanide 
 Sodium Cyanide 
 Sodium Carbonate 
 
 Cyanide/Carbonate Sludge 
 Waste Rinsewater 
 Sludge/Solids 
 
 Chromate 
 
 Various Chromating Spent Chromate Solution 
 
 Chemicals, Most Contain Waste Rinsewater 
 
 Hexavalent Chromium Compounds 
 
 Apply Polyseal 
 
 Proprietary Seal 
 (Organic Material) 
 
 Clean-up 
 
 And Stripping Waste 
 
 B. KEYS TO SUCCESSF UL ELECTROPLATING _ 
 
 Keys To Successful Electroplating : 
 
 * Customized pre-plate cycle 
 Knowledge of metallurgy 
 
 * Knowledge of substrate condition 
 
 The above exannples illustrate that the bulk of wastes and of hazardous wastes are 
 generated from the electroplating operation and the operations ancillary to electroplating. 
 The types of wastes generated depend upon the metals/alloys to be electroplated and the 
 types of metals plated onto the substrate(s). 
 
 © 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 6 
 
Before any part can be electroplated it must be properly "prepared". In fact, the "secret" 
 to being a successful electroplater is in the knowledge of how to clean and prepare a 
 substrate for plating. An improperly prepared substrate typically results in poor adhesion 
 of the plated metal, resulting in peeling and or blistering. When properly prepared, the 
 plated metallic layer will have about the same adhesion to the substrate as the individual 
 metal atoms within the substrate have to themselves). There are some exceptions to this, 
 notably plated metals on plastics, and metals that have a perpetual layer of tenacious 
 oxide, such as aluminum, magnesium, titanium and stainless steels. Preparing the part for 
 plating is typically performed in a series of tanks and rinses referred to as the "pre-plate 
 cycle". 
 
 The preplate cycle typically is customized to the type of substrate that is to be plated. It 
 may involve degreasing the part, then cleaning and acid pickling it, or it may be far more 
 complicated. The following are common process steps used to electroplate different 
 types of metal surfaces (vapor degrease is not included, but may be required). Note that 
 wherever a new processing step (not covered above) is indicated, additional waste is 
 generated in the form of spent solution and rinsewater: 
 
 Processing Sequence, Leaded Brass; 
 
 Step/Waste Generated: 
 
 Cathodic Clean/Spent Cleaner, oils, Sludge From Tank Bottom 
 RInse/Contamlnated Rinsewater 
 
 Anodic Clean/Spent Cleaner, Oils, Sludge From Tank Bottom 
 
 RInse/Contamlnated Rinsewater 
 
 Fluoboric Acld/Spent Acid 
 
 RInse/Contamlnated Rinsewater 
 
 Copper Strike/Contaminated Filtration Media 
 
 Rinse Contaminated Rinsewater 
 
 Copper Plate/Contamlnated nitration Media 
 
 RInse/Contamlnated Rinsewater 
 
 Dry _ 
 
 Note: For non leaded brass and copper or copper alloys, substitute acid salts or sulfuric 
 acid for fluoboric acid. 
 
 Processing Sequence, Zinc Die Castings; 
 
 Step/Waste Generated: 
 
 Soak Clean/Spent Cleaner, oils. Sludge From Tank Bottom 
 
 Anodic Clean/Spent Cleaner, Oils, Sludge From Tank Bottom 
 
 RInse/Contamlnated Rinsewater 
 
 Dilute Acld/Spent Acid 
 
 RInse/Contamlnated Rinsewater 
 
 Copper Strike/Contamlnoted Filtration Media 
 
 Rinse Contaminated Rinsewater 
 
 Plate/Waste Depends On Type Of Plating Performed 
 
 RInse/Contamlnated Rinsewater 
 
 Note: A high pH nickel plate may be an alternate to the cyanide copper strike, but may 
 pose some operational problems. 
 
 © 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 7 
 
Processing Sequence, Case Hardened Steel/High Carbon Steel: 
 
 Process Step/Waste Generated; 
 
 Soak Clean/Spent Cloaner, Oils, Sludges From Tank Bottom 
 Anodic Clean/Spent Cleaner, oils, Sludge From Tank Bottom 
 Rlnse/Contamlnoted RInsewater 
 Hydoichloric Acid/Spent Acid 
 Rinse/Contamlnoted RInsewater 
 
 Cathodic Clean/Spent Cleaner, Oils, Sludges From Tank Bottom 
 
 Rlnse/Contamlnoted RInsewater 
 
 Hydrochloric Acld/Spent Acid 
 
 Rinse Contaminated RInsewater 
 
 Anodic Etch/Spent Acid 
 
 Rlnse/Contamlnoted RInsewater 
 
 Pkite/Waste Depends on Type of Plating Applied 
 
 Rlns /Contaminated RInsewater 
 
 Dry 
 
 Note: Woods nickel strike may be substituted for Anodic Etch (Woods Nickel strike 
 contains 250 g/L Nickel chloride plus 125 ml/L hydrochloric acid, ) 
 
 Processing Sequence, Aiuminum or Magnesium: 
 
 Process Step/Waste Generated; 
 
 Soak Clean/Spent Cleaner, Oils, Sludges From Tank Bottom 
 Rlnse/Contamlnoted RInsewater 
 Nitric Acld/Spent Acid 
 Rlnse/Contamlnoted RInsewater 
 Zlncote/Spent ZIncate Solution 
 Rinse/Contaminated RInsewater 
 Copper Strike/Contaminated Filtration Media 
 Rlnse/Contamlnoted RInsewater 
 Plate/Waste Depends on Type of Plating Applied 
 Rlnse/Contamlnoted RInsewater 
 Dry 
 
 Notes: Add bifluoride salts to nitric if the aluminum alloy contains silicon. If the parts are 
 magnesium, substitute a solution of 10% Ammonium bifluoride in 20% phosphoric acid 
 for the nitric acid, and substitute a pyrophosphate zincate for the normal zincate. 
 Pyrophosphate zincate contains 1-1.6 oz/gai zinc sulfate plus 10-12 oz/gal sodium 
 pyrophosphate. The bath operates at 170-180 deg. F, and the immersion coating forms 
 in 3-5 minutes. 
 
 © 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 8 
 
# 
 
 r 
 
 Metal Finishing Process Overview cu^^ • # cu° 
 
 
 Metal finishing Process Overview o;' • — • 0.° 
 
 Processing Sequence, 400 Series Stainless,lnconel, Hastelloy; 
 Process Step/Waste Generated; 
 
 Soak Clean/Spent Cleaner, Oils, Sludges From Tank Bottom 
 Rlnse/Contomlnoted Rinsewoter 
 
 Cathodic Cleon/Spent Cleaner, Oils, Sludges From Tank Bottom 
 Rinse/Contomlnoted Rinsewoter 
 
 Hydrochloric Acld/Spent Acid 
 
 Rlnse/Contomlnated Rlnsewoter 
 
 Anodic Wood’s Nickel Strlke/Contomlnoted Filtration Medio 
 Rlnse/Contomlnoted Rlnsewoter 
 
 Cathodic Wood’s Nickel Strlke/Contomlnoted Filtration Medio 
 Rlnse/Contomlnoted Rlnsewoter 
 
 Plote/Woste Depends on Type of Plating Applied 
 Rlnse/Contomlnoted Rlnsewoter 
 
 Dry 
 
 Processing Sequence, 300 Series Stainiess,Monei, Tooi Steeis; 
 Process Step/Waste Generated; 
 
 Sook Cleon/Spent Cleaner, Oils, Sludges From Tank Bottom 
 Rinse/Contomlnoted Rlnsewoter 
 
 Cothodic Cleon/Spent Cleoner, Oils, Sludges From Tonk Bottom 
 Rlnse/Contomlnated Rlnsewoter 
 
 Hydrochloric Acld/Spent Acid 
 
 Rlnse/Contomlnated Rlnsewoter 
 
 Anodic In 25% Sulfuric Acld/Spent Acid 
 
 Rlnse/Contomlnoted Rinsewoter 
 
 Cathodic Wood's Nickel Strlke/Contomlnoted Filtration Medio 
 Rlnse/Contomlnoted Rlnsewoter 
 
 Plote/Waste Depends on Type of Plating Applied 
 Rinse/Contomlnoted Rinsewoter 
 
 Dry 
 
 Processing Sequence, BerylliumAellurium Copper; 
 
 Process Step/Waste Generated; 
 
 Soak Clean/Spent Cleaner, Oils, Sludges From Tank Bottom 
 
 Rinse/Contomlnoted Rlnsewoter 
 
 Sulfuric-Nitric Bright Dip/Spent Acid 
 
 Rinse/Contamlnoted Rlnsewoter 
 
 Hydrochloric Acid (50%)/Spent Acid 
 
 Rlnse/Contomlnoted Rinsewoter 
 
 Ammonium Persulfote/Spent Solution 
 
 Rlnse/Contomlnoted Rlnsewoter 
 
 Copper Strlke/Contomlnoted Flltrotion Medio 
 
 Rlnse/Contomlnoted Rinsewoter 
 
 Plote/Woste Depends on Type of Plating Applied 
 
 Rlnse/Contomlnoted Rinsewoter 
 
 Dry 
 
 Note: brite dip: 2 gal Sulfuric Acid plus 1 gal Nitric Acid plus 1/2 fl oz Hydrochloric acid. 
 No Water. Optional substitute: 20-30 % Sulfuric acid at 160-180 deg F. 
 
 I Metal Finishing Process Overview c-' • — • cu° 
 
 
 II Metal Finishing Process Overview # cu° 
 
 Processing Sequence, Bronzes: 
 
 
 Processing Sequence, Titanium; 
 
 Process Step/Waste Generated; 
 
 
 Process Step/Waste Generated; 
 
 Soak Cleon/Spent Cleaner, Oils, Sludges From Tank Bottom 
 Rlnse/Contomlnoted Rlnsewoter 
 
 Cothodic Cleon/Spent Cleaner, Oils, Sludges From Tank Bottom 
 Rlnse/Contomlnoted Rlnsewoter 
 
 Hydrochloric Acid (15%)/Spent Acid 
 
 Rlnse/Contomlnoted Rlnsewoter 
 
 Nitric Acid (7S%)/Spent Acid 
 
 Rlnse/Contomlnot^ Rlnsewoter 
 
 Copper Strlke/Contomlnoted Filtration Medio 
 
 Rlnse/Contomlnoted Rlnsewoter 
 
 Plote/WOste Depends on Type of Plating Applied 
 Rinse/Contomlnoted Rlnsewoter 
 
 Dry 
 
 
 Blast Cleon/CoiTtamincited Blasting Medio 
 
 Hydrochloric Acid (20%)/Spent Acid 
 
 Rlnse/Contomlnoted Rinsewoter 
 
 Electroless Nickel Plote/Spent Plating Solution/NItrIc Acid Waste 
 Rlnse/Contomnloted Rlnsewoter 
 
 Nickel Ptote/Contomlnoted Filtration Medio 
 
 Rlnse/Contomnloted Rlnsewoter 
 
 Diffuse/None 
 
 Sulfuric Acid (25%)/Spent Acid 
 
 Rlnse/Contomlnoted Rlnsewoter 
 
 Plote/Woste Depends on Type of Plating Applied 
 
 Rlnse/Contomlnoted Rlnsewoter 
 
 Dry 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 9 
 
C. Process Step Details 
 
 The following are details of commonly employed processing steps indicated above: 
 
 1. PRE-CLEANING - to avoid solution contamination and obtain coating 
 adhesion 
 
 A. Vapor degreasing 
 
 B. Pickling/Descaling/Blasting 
 
 C. Soak Cleaning 
 
 1. PRE-CLEANING 
 
 Most metal parts are covered with grease or oil during their manufacture, by operations 
 such as stamping, drilling, forging, buffing, and polishing. Heat treated steel parts may 
 have a "scale" of iron oxides (rust) that would interfere with the appearance and 
 adhesion of the plated coating. Other ferrous based parts may have some rust due to 
 unprotected storage. This "soil" must be removed by the metal finisher to avoid 
 contamination of his processing solutions and to obtain adhesion of the coating to the 
 plated part. Pre-cleaning refers to the processing a metal finisher may perform on 
 parts before they are routed through the plating line. Pre-cleaning is typically 
 accomplished in one or a combination of the following procedures: 
 
 • 
 
 A. Vapor Degreasing 
 
 A vapor degreaser typically consists of a stainless steel tank with a compartment at the 
 bottom for boiling one of several solvents, such as trichloroethylene, perchloroethylene, 
 methylene chloride, Freon, or 111 Trichloroethane. The boiling solvent creates a vapor 
 zone within the walls of the tank. The vapors are condensed using cooling coils 
 near the top of the tank. There are several variations of how to vapor degrease but the 
 basic principle involves hanging the greasy parts in the vapor zone on stainless steel 
 hooks or wire. Larger degreasers for small parts are automated and the parts enter in ^ 
 steel trays and are automatically routed through the equipment. Since the parts entering 
 
 ® 1994 Frank Attmayer, Scientific Control Labs. Inc. 
 
 Page 10 
 
the degreaser are cooler than the vapor, the solvent condenses on the parts and flushes 
 off the oil/grease. The parts emerge from the degreaser in a relatively dry state, although 
 some solvent may be trapped in pockets or drilled holes. The solvent/oil mixture returns 
 to the boiling chamber, where the solvent is re-boiled, while the oil/grease remains in the 
 mix. Eventually, the oil/solvent mix must be removed, replaced, and disposed of. 
 
 Pickling/Descaiing/Blasting 
 
 Heavy Scale/Rust-Pickling or Blasting 
 
 Pickling: Strong Acid (eg. Hydrochloric) 
 Descaling: Alkaline-Permanganate 
 Strong Acid 
 
 Blasting: Last Resort (Expensive) 
 
 Normal in Hard Chromium 
 Plating Operations 
 
 B. Pickling/Descaiing/Blasting 
 
 Heavily rusted or scaled parts need to be processed through an operation that removes 
 the heavy oxide from the surface of the part. There are a number of ways to accomplish 
 this, including blasting with nutshells, sand, or other "grit", pickling in strong solutions of 
 acids, or descaling in an alkaline descaling solution consisting of concentrated sodium 
 hydroxide and potassium permanganate at high temperature. Pickling and descaling is 
 normally performed "off-line", because they are time consuming operations. The 
 operation generates spent pickle liquor/descaling solution or contaminated blasting media. 
 
 II Metol Finishing Process Ovetyiew c:'#>.cu°o 
 
 Typical Cleaning Tank With Continuous Oil Removal 
 
 Tap To Remove Free Oil 
 
 C. Soak Cleaning 
 
 A soak cleaning tank typically consists of a steel tank containing a cleaning solution 
 consisting of strong alkalies, various other ingredients and detergents mixed with water 
 
 © 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 11 
 
at temperatures from 160-200 deg. F. The parts to be cleaned are racked or in plating A 
 barrels and are immersed in the cleaning solution and the oil and grease is either 
 emulsified or converted to soaps through saponification. The parts emerge from the soak 
 cleaner coated with hot cleaner that then is either rinsed off before further processing, or 
 is dragged into the next process. Soak cleaners are normally incorporated into the plating 
 process line and are usually the first tank the parts go into, so they may also be 
 considered part of the Pre-Plate operations described below. Soak Cleaners have a finite 
 life due to the consumption of ingredients and accumulation of floating and dispersed 
 oils, greases and organic compounds. Many soak cleaners employ skimming devices to 
 remove floating oil.grease, in an effort at extending the life of the cleaner. Modern 
 ultrafiltration systems have also been developed to remove contaminants so that the 
 cleaner lasts much longer. 
 
 PRE-PLATE OPERATIONS 
 
 * Needed due to reduction of cyanide use 
 
 * Removes last traces of soils and oxides 
 
 CLEANING - Electrocleaning follows degreasing or soak cleaning 
 
 Electrocleaner & DC current decomposes H 2 O into H & 0 
 Direct (parts neg. charged) or Reverse (parts pos. charged) 
 Followed by rinse water 
 
 ACID DIP/PICKLES - Neutralize alkali and remove surface oxides 
 Followed by rinse water 
 
 SPECIAL DIPS - Prevent reformation of oxides when exposed to air (aluminum) 
 
 STRIKES - Solution that provides thin protective coating of metal that will not 
 react with the plating solutions 
 
 2. PRE-PLATE OPERATIONS 
 
 Pre-cleaning removes the bulk of the oils, greases, rust, scale or other soils present on 
 the parts. In "the old days", when most plating solutions contained large concentrations 
 of cyanide, pre-cleaning often was all that was required prior to plating. Modern metal 
 finishing operations have replaced many cyanide solutions with non-cyanide chemistries 
 and have reduced cyanide concentrations in those processes where cyanide remains, so 
 pre-cleaning is not enough to prepare the parts for plating. The pre-plate operations must 
 be tailored to the type of metal processed and the conditions of the surface of the parts. 
 The object of the pre-plate process is to remove the last traces of surface soils and to 
 remove all oxides from the surface. The following pre-plate processing steps are typical: 
 (vapor degrease is not included, but may be required). Note that wherever a new ^ 
 
 processing step is indicated, additional waste is most often generated: ^ 
 
 © 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 12 
 
II ^tetal Finishing Process Ovetview c:'>».cu°o 
 
 Electrocleaning Process 
 
 In Cathodic 
 Cleaning, The 
 Parts Are 
 
 Negatively Charged 
 (As Shown) 
 
 In Anodic Cleaning, 
 The Charges Are 
 Reversed 
 
 Parts To 
 Be Cleaned 
 
 Oxygen Gas Is 
 Evolved At The 
 Anode (Positive 
 Electrode) 
 
 Hydrogen Gos Is 
 Evolved At The 
 Cathode 
 (Negottve Electrode) 
 
 Rack To Hold Parts 
 
 3. CLEANING 
 
 Degreased parts still require additional cleaning to remove traces of soils left behind by 
 the pre-cleaning step. This is normally accomplished by an electrocleaning operation. 
 Electrocleaning systems consist of a heated steel tank that contains a solution similar to 
 the soak cleaner. The tank is equipped with a rectifier and steel or stainless steel 
 electrodes hanging from bus bars on either side of the tank. Cleaning is normally the next 
 process step after degreasing or soak cleaning. If the parts were vapor degreased, they 
 are either racked on plating racks or scooped/shoveled into plating barrels for cleaning. 
 The racks or barrels are immersed into the electrocleaner and a DC current is passed 
 through the parts. The current decomposes the water into two gases, oxygen and 
 hydrogen. It is these gases, which are discharged in finely divided bubbles that do the 
 cleaning. If the parts to be cleaned are negatively charged during this process, then 
 hydrogen bubbles (commonly referred to as "direct" cleaning) are generated on the parts. 
 If the parts are positively charged (commonly referred to as "reverse" cleaning), then 
 oxygen bubbles perform the cleaning task. In each case the opposing electrode generates 
 the other gas. The choice of direct vs reverse cleaning depends upon the type of metal to 
 be cleaned, and its tendency to react with oxygen to form an oxide or the tendency for 
 direct cleaning to deposit smuts. Both direct and reverse cleaning are sometimes 
 performed either in sequence, with a periodic reverse rectifier, or through use of a 
 rectifier and a reversing switch. Following electrocleaning, the parts are rinsed in water. 
 Electrocleaner solutions have a finite life also, and typically need to be disposed of on a 
 regular basis. Ultrafiltration and oil skimming on these cleaners can also be effective at 
 increasing cleaner life. 
 
 © 1994 Frank Altmayer, Scientific Control Labs, Inc, 
 
 Page 13 
 
I Metal Finishing Process Ovemew cu°o 
 
 Acid Dip/Pickle 
 
 The Purpose of The Acid Dip Is to Remove The Alkaline Film From 
 Cleaners, and Dissolve Off Any Light Corrosion Products (Oxides) 
 
 Part To Be Plated 
 
 -Alkaline Film 
 
 Corrosion Products 
 
 4. ACID DIP/PICKLES 
 
 Parts that have been electrocleaned still have a thin alkaline film remaining, even after 
 prolonged rinsing. This film must be removed for adequate adhesion to take place in the 
 plating tank. Additionally, the parts may have a thin oxide film either formed during 
 electrocleaning, or formed by exposure of the clean metal to air. This oxide also must be 
 removed in order to obtain adequate adhesion of the plating. Lastly, some metals contain 
 alloying elements that interfere with good adhesion. An example is lead which is added to 
 brass to enhance the machining properties of the brass. The lead in the brass forms 
 oxides that are not removed by the acids that are normally used before plating, such as 
 sulfuric and hydrochloric. A special acid must be used to remove lead oxide from the 
 surface of such brasses. The acid dip must therefore be of a chemistry that will neutralize 
 alkali, and remove all surface oxides present on the part to be plated. After the acid dip, 
 the parts are rinsed in water. 
 
 Acid dips and Pickles are consumed by neutralization of the acidity and the life of these 
 dips is reduced by contamination with dissolved metals. The acids must periodically be 
 disposed of through the waste treatment system. The life of an acid dip can sometimes 
 be extended by careful control of dropped parts, use of acid sorption recovery methods, 
 and control of acid strength (high strength dissolves too much base metal). 
 
 I Metol Finishing PiocessOvetview c:’ 
 
 Cu 
 
 Special Dips, Exampies; 
 
 1. Zincote For Aluminum/Magnesium 
 
 2. Sulfuric/NItrIc Bright Dip For Copper PAits 
 
 3. Phosphoric/Nitric Bright Dip For Aiuminum Parts 
 
 Strikes: 
 
 Pui 
 
 Electrogalvanically and 
 
 Purpose Is To Eliminate Immersion Deposits That Form 
 
 Adversely Affect Adhesion 
 
 Secondary Pupose Is To Act As 'Catch-Basin' for Impurities 
 And Therefore Protect The More Valuable 'Plate' Solution 
 
 © 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 14 
 
5. SPECIAL DIPS 
 
 Some parts are made of metals that re-form oxides as soon as the metal is exposed to 
 air. An example is aluminum. Aluminum parts can be cleaned and acid dipped before 
 plating and the plating will still not adhere, because the aluminum forms an oxide by 
 reacting with the air as soon as the parts is removed from the acid, rinsed, and exposed 
 to air. A special dip is therefore needed to prevent this from happening. The cleaned and 
 acid dipped aluminum is dipped into a solution of sodium hydroxide and zinc oxide (often 
 other ingredients are added) and water. In this solution, a controlled galvanic reaction 
 occurs, where some of the aluminum dissolves and at the same time, some of the zinc 
 coats the aluminum with a very thin film of zinc. The part that leaves this dip (called a 
 zincate) is now coated with zinc, so there is no aluminum surface to react with the air. 
 Special dips are subject to contamination and weakening through use. They therefore 
 have a finite life and must be disposed of as concentrated wastes. 
 
 6. STRIKES 
 
 Some parts are made out of metals that react galvanically with certain plating solutions. 
 An example is a zinc die casting or an aluminum part that has been dipped into a zincate. 
 If we want to plate the zinc part, most plating solutions will chemically or galvanically 
 attack the zinc. We therefore must use a specially designed solution called a "strike" to 
 apply a thin protective coating of metal that will not react with the plating solutions. For 
 zinc, or zincated aluminum, such a strike typically is a cyanide copper strike solution 
 (described later). Some metal can not be adherently plated without first applying a thin 
 strike deposit from a specialized strike plating solution. An example is stainless steel, 
 which has a rapidly forming oxide that must be simultaneously removed in a special 
 nickel strike solution, while a thin film of nickel is deposited over the stainless steel to 
 prevent the reformation of the oxide. The nickel strike solution is purposely formulated to 
 yield a thin deposit, while generating a large amount of hydrogen that reacts with the 
 oxide on the stainless steel. Strike plating solutions are typically formulated to have a 
 long life, lasting many years, unless contamination occurs. These solutions are very 
 difficult to purify, when contaminated above tolerable concentrations, and at that time 
 become wastes that require disposal. 
 
 Meta finishing Process Overview c:’ 
 
 o 
 
 Plating Step: 
 
 Example Of Single Deposit: Hard Chromium Plate Over Steel Shaft 
 
 Example Of Multiple Deposit: Copper Plus Nickel Plus Chromium 
 
 Over Zinc Die Casting Or Steel 
 Nickel Plus Gold Over Brass For 
 Jewelry Or Electronics 
 
 Plating Solutions For Electroplating; Long Life (Many Years) 
 Strike Plating Solutions: Medium Lite (Years) 
 
 Electroless Plating Solutions: Short Life (Weeks/Months) 
 
 Spent Plating Solutions Pose Difficult Disposal Problem 
 
 © 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 15 
 
7. PLATE 
 
 The plating step may be a single plate or a series of different deposits. If a series of 
 deposits is to be applied, there usually is a rinse and an acid dip between the different 
 plating steps. For example, a zinc die casting may be plated with a cyanide copper strike, 
 followed by a cyanide copper plate, followed by a semi-bright nickel plate followed by a 
 bright nickel plate followed by a thin deposit of chromium. No rinsing or acid dipping may 
 be required between the cyanide copper strike and the cyanide copper plate, or the semi 
 bright nickel and the bright nickel, because the chemistries of the sequential baths are 
 similar. However, there will be a rinse and an acid dip between the cyanide copper plate 
 and the semi-bright nickel because one solution is alkaline and the other is acidic. There 
 will be a rinse between the bright nickel plate and the chromium plate to prevent 
 contamination of the chromium plating solution with nickel. There may or may not be an 
 acid dip, since both solutions are acidic. After all plating has been performed the parts are 
 rinsed and dried before packaging them for shipment. 
 
 Most plating solutions are formulated to provide a long life (many years), as long as 
 impurities are periodically removed (creating waste), and reasonable care is taken by the 
 plater to not contaminate the solution with excessive concentrations of contaminants. 
 Certain plating solutions (especially "non-cyanide" versions of cyanide formulations) are 
 very sensitive to metallic contamination and may have reduced life. 
 
 All electroless plating solutions have a relatively short life span, when compared to 
 electroplating solutions (months vs years). All spent plating solutions are very 
 concentrated and pose waste treatment difficulties/hazards. They typically are sent off 
 site for disposal or heavily diluted prior to in-house treatment.. 
 
 I Metal Finishing PfocessOvenfiew c:’>>.cu°o 
 
 Post Ploting/Anodizing Processing Operations: 
 
 1. Bright Dipping 
 
 2. Chromcrting 
 
 3. Lacquering 
 
 4. Appiication of Wax 
 
 5. Dying 
 
 6. Sealing 
 
 _ 7. Coloring/Antiqueing _ 
 
 8. POST PLATING PROCESSING 
 
 Some plated parts are further processed to yield additional corrosion protection or to 
 change the color of the deposit. Examples of such further treatment include the 
 application of waxes or lacquers (see "polyseal" in example 4) to enhance the tarnish 
 resistance and chromate conversion coatings following zinc, cadmium or other plated 
 deposits to yield chromate films that range in color from transparent to olive drab greem 
 Brass plating is often treated with various chemical solutions to turn the brass to differ^ 
 colors ranging from green to black (even red is possible). All such subsequent treatments 
 
 © 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 16 
 
typically involve dipping the rack or plating barrel in one or more chemical solutions in 
 various tanks and then rinsing off those solutions. Such solutions often contain 
 ingredients such as nitric acid, sodium dichromate, selenium, arsenic, antimony, or other 
 hazardous ingredients. The processing tanks and associated rinses may be incorporated 
 into the plating line, or the operation may be carried out "off-line". 
 
 End Chapter 2 
 
 © 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 17 
 
Table of Contents 
 
 III. Metal Finishing Process Details 
 
 Topic 
 
 Overview 
 
 Choosing the right plated coating 
 
 Plating lines/department 
 
 Methods of Plating; Rack plating 
 
 Barrel plating 
 Continuous plating; Strip 
 
 Reel to reel 
 
 Hardware; Tank 
 
 Rectifier 
 
 Filter 
 
 Heating equipment 
 
 Agitation 
 
 Ventilation 
 
 The Plating Solution; Zinc 
 
 Cadmium 
 
 Copper 
 
 Brass 
 
 Bronze 
 
 Zinc-alloy 
 
 Nickel 
 
 Chromium 
 
 Gold 
 
 Silver 
 
 Tin 
 
 Tin-lead alloy 
 Electroless Processes 
 Chromating 
 
 Page Number 
 
 1 
 
 2 
 
 5 
 
 6 
 7 
 
 10 
 
 11 
 
 12 
 
 12 
 
 13 
 
 13 
 
 14 
 14 
 
 16 
 
 18 
 
 19 
 
 22 
 
 22 
 
 23 
 
 24 
 27 
 29 
 31 
 31 
 
 33 
 
 34 
 36 
 

 •r 
 
 to ^Wi>T 
 
 
 
 * ' * 
 
 
 
 <0 
 
 ;^r'..' I ,. ‘--/IS?.7 irl0jt ■■'■ 
 
 ’' .nT 
 
 
 
 l'- ‘'■,! '"if A 
 
 rV;! ' '?- 
 
 }4\^: 
 
 
 
 ■_ ?5iiiSA ♦I'fhllto® 
 
 fUtl^b: 
 
 S '". ■S '- 
 
 V 
 
Part III, 
 
 Metal Finishing Process Details 
 
 The metal finishing industry provides a vital public service; that of protecting all kinds of 
 metals (and non metals) from corrosion, excessive wear, or electrical malfunction. 
 
 Metal finishing is more than electroplating. It is the creation of a coating/coatings on a 
 metal or non metal substrate by chemical, electrochemical, or physical means. The 
 following processes are typical metal finishing operations: 
 
 ntroduclionlo Metal Finistiing 
 
 #cu° 
 
 Typical Metal Finishing Operations: 
 
 
 
 Electroplating 
 
 Electroless Plating 
 
 Anodizing 
 
 PhosphoTlng 
 
 Conversion Coating 
 
 Painting 
 
 Powder Coating 
 
 Electropainting (E-Coot) 
 Burnishing 
 
 Electrop<»ishlng 
 
 Chemical Milling/Etching 
 Vacuum Metallizing 
 Mechanical Plating 
 
 
 Overview Of The Metal Finishing Industry 
 
 3,000 "Job Shops' 
 
 14,000-30,000 'Captive Shops' 
 
 SIC 3471 
 
 Regulated Under: 
 
 Clean Air 
 
 Clean Water 
 
 RCRA/SARA/CERCLA 
 
 OSHA 
 
 EPCRA 
 
 Numerous Other Federal, State, Local Regulations 
 
 In the United States, there are approximately 3,000 small companies that perform "job 
 shop" electroplating. They are considered a service industry, in that they take parts 
 manufactured by others, apply a metal finishing process or processes to those parts, and 
 then return them to their client. In addition to job shop metal finishers, there also are 
 "Captive" metal finishing facilities. Captive facilities are typically owned by large 
 corporations and perform metal finishing processes as part of the manufacture or 
 overhaul of a product manufactured by the large corporation. There is no accurate 
 estimate of how many captive metal finishing facilities exist in the United States today. 
 Estimates from 14,000 to 30,000 have been given in the past. 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 1 
 
All metal finishing facilities are regulated on a national and local level under numerous 
 agencies enforcing various regulations, including the Clean Water Act, RCRA (Resource 
 Conservation and Recovery Act), SARA (Superfund Amendments and Re-authorization Act' 
 CERCLA (Comprehensive Environmental Response, Compensation and Liability w 
 
 Act), EPCRA (Emergency Planning and Community Right To Know Act), the Clean Air Act, 
 and OSHA (Occupational Safety and Health Act). 
 
 In order to comply with provisions of the Clean Water Act, most metal finishing companies 
 operate pretreatment systems to remove pollutants before their process water is discharged 
 either to a stream (under NPDES permit) or to a sewer system (under discharge 
 authorization from the POTW). These pretreatment systems typically generate a solid waste 
 that is regulated under RCRA. 
 
 Most metal finishing facilities utilize toxic/hazardous chemicals that are regulated under 
 OSHA, CERCLA, EPCRA, and SARA. These include cyanides, various acids, strong 
 alkalies, powerful oxidizers, and numerous flammable and non flammable organics. 
 
 ELECTROPLATING 
 
 CHOOSING THE RIGHT PLATED COATING 
 
 The choice of what metal(s) are to be plated on a part is usually made by the design 
 engineer at the manufacturing site. Plated and chemically applied coatings are typically 
 applied to enhance one of the following properties: 
 
 lntfO(Juction lb Metal Finishing cr/’© 
 
 ^Cu° 
 
 Typical Properties Achieved Through Electroplatiitg: 
 
 
 
 Corrosion Resistance 
 Appearance 
 
 Abrasion Resistance 
 
 Value (eg Sllver/Gold Plate) 
 Solderability 
 
 Rubber Bonding 
 
 Electroforming 
 
 Electrical Resmance 
 
 Reflectivity 
 
 Diffusion Barrier 
 
 Lubricity 
 
 High Temperature Resistance 
 
 
 The designer will usually find that there is not much choice as to which combination of 
 coatings is the best for his/her application. The plating combination that will provide the best 
 compromise of cost vs the above benefits will usually be that specified for the part. The 
 designer will then create a "specification" for the part that will detail the type of plating, the 
 thickness range that each plated layer is to have, special properties (hardness, solderability 
 etc.) that the plating is to have, and the subsequent coatings, if any, that are to be applied 
 after plating. The following are typically plated metals and alloys and the possible reasons 
 for specifying them: ^ 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 2 
 
PLATED METAL 
 
 BENEFICIAL PROPERTY 
 
 COMMON USES 
 
 Zinc 
 
 Inexpensive Corrosion 
 Protection 
 
 Hardware, Fasteners 
 Automotive 
 
 Zinc-Alloy 
 
 (Co, Ni, Sn, 
 
 Fe) 
 
 Superior Corrosion 
 Protection, 
 
 Cadmium Substitute 
 
 Cadmium 
 
 Corrosion Protection 
 Lubricity 
 
 Solderability 
 
 Anti-fouling 
 
 Electronics, Hardware 
 Fasteners, Aerospace 
 Weapons 
 
 Automotive 
 
 Copper 
 
 Ductile Underlayer 
 Decorative 
 
 Conductivity 
 
 Diffusion Barrier 
 
 Electrical cable. 
 Pennies, Die Castings 
 Electronics, 
 
 Carburizing 
 
 Electroforming 
 
 Automotive 
 
 Plated Plastics 
 
 Circuit Board Mfg. 
 
 Brass 
 
 Decorative 
 
 Promotes Adhesion Of 
 Rubber To Steel 
 
 Furniture, Hardware 
 Vulcanizing, Consumer 
 Items 
 
 Bronze 
 
 Decorative 
 
 Lubricity 
 
 Consumer Goods, 
 Bearings 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 3 
 
PLATED METAL 
 
 Nickel 
 
 BENEFICIAL PROPERTY 
 
 Decorative 
 
 Wear Resistant 
 Anti-Tarnishing 
 
 Corrosion Resistant 
 
 COMMON USES 
 
 Consumer Goods 
 Electroforming 
 
 Electronics 
 
 Tools 
 
 Automotive 
 
 Plated Plastics 
 
 Circuit Board Mfg. 
 
 Chromium 
 
 Wear Resistant 
 
 Anti-Tarnish 
 
 Decorative 
 
 Consumer Goods 
 Aerospace 
 
 Automotive 
 
 Heavy Equipment 
 
 Gold 
 
 Low Electrical Resistance 
 Anti-Tarnish 
 
 Decorative 
 
 Electronics 
 
 Aerospace 
 
 Automotive 
 
 Jewelry 
 
 Printed Wiring Boards 
 
 Silver 
 
 Electrical Conductivity 
 Appearance 
 
 Solderability 
 
 Electronics 
 
 Jewelry 
 
 Home Furnishings 
 
 Tin 
 
 Corrosion Resistance 
 Solderability 
 
 Ductility 
 
 No Toxicity 
 
 Steel Stock For Cans etc. 
 Electronics 
 
 Circuit Board Mfg. 
 
 Food Utensils 
 
 Tin-Lead 
 
 Solderability 
 
 Corrosion Resistance 
 
 Electronics 
 
 Circuit Board Mfg. 
 
 There are numerous other metals and alloys that can be plated to obtain specific benefits. 
 These include precious metals other than gold and silver (Rhodium, Palladium, Ruthenium, 
 Platinum), and some uncommon "common" metals and alloys such as Bismuth, Iron, 
 Alballoy (Copper-Tin-Zinc). There are also "composite coatings" that can be plated. For 
 example, one can plate a nickel-cobalt alloy containing finely dispersed particles of silicon 
 carbide to enhance abrasion resistance. This, or a some other composite may one day be a 
 substitute for chromium plating. 
 
 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 4 
 
Ill Metal Finishing Process Details cu • —► • cJ 
 
 Zinc Plating Line: 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Soak Electro- Rinse Acid Rinse Plate 
 
 Clean clean 
 
 PLATING LINES/DEPARTMENT 
 
 Except for vapor degreasing, which normally is performed off-line, plating operations are 
 normally incorporated into a sequence of tanks, called a "line". 
 
 A plating line may be designed to produce a single coating or a number of coatings. While 
 not always the case, the process line contains tanks lined up in sequential order. Automated 
 lines may or may not contain tanks in sequential order. 
 
 A zinc plating line may therefore consist of 13 tanks, each containing a chemical processing 
 solution or rinse water; soak clean, electroclean, rinse, acid, rinse, zinc plate, rinse, bright 
 dip, rinse chromate, rinse hot water rinse, dry. If the line is for barrel plating, each tank may 
 have one or more "stations", that is places to put a barrel. A six station zinc plating tank can 
 plate six barrel loads of parts at one time. To economize, some shops may have one 
 cleaning line that services several plating lines. There also are tanks for rack stripping, 
 stripping rejects, purifying contaminated solutions or holding solutions that are only 
 sporadically used. The entire lineup of tanks and lines creates a "layout" of the shop, with 
 parts entering the plating department from one direction, travelling through the process 
 lines, and leaving the plating department. 
 
 THE ELECTROPLATING PROCESS 
 
 Electroplating is a process for coating a metallic or non metallic substrate, with a metallic 
 coating through the use of a combination of electricity and a chemical solution that includes 
 the ions of the metal in the coating. To conduct the process, we first need to purchase some 
 hardware. 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 5 
 
Simple electroplating hardware consists of: 
 
 III Metal Finishing Process Detoils 
 
 • cu° 
 
 Simple Electroplating Hardware 
 
 Rack or Barrel To Hold parts and Make electrical connection 
 Tank to contain plating solution and accessories 
 A power supply such as a DC generator, battery, or rectifier 
 Filtration equipment (optional in some plating processes) 
 Agitation Equipment (optional in some plating processes) 
 Ventilation Equipment (may be optional) 
 
 Plating Solution 
 
 Other processing tanks for cleaning, rinsing, acid pickling 
 and waste treatment 
 
 METHODS OF PLATING 
 
 Plating can be performed using three main methods of part handling, each requiring 
 different hardware: 
 
 III Metal finishing Process De tails cu*' »—• cu” 
 
 Rack Plating: 
 
 III Metal Finishing Process De toils 
 
 Rack Plating: 
 
 Illustrations Courtesy of Belke Mfg. Chicago IL 
 
 A. RACK PLATING METHOD 
 
 Rack plating is sometimes referred to as still plating and is used whenever the parts are too 
 large, delicate or complicated to be barrel plated. Rack plating is much more expensive than 
 barrel plating because of the labor involved in putting the parts on the rack and taking them 
 off after they are processed. Rack plating is performed by hanging the parts to be plated on 
 "racks", which are typically plastic coated copper or aluminum rods, with stiff wires/hooks 
 that hold the parts in place and make electrical contact, protruding at various intervals. 
 
 Racks come in numerous designs and are most often constructed by outside vendors and 
 sold to the metal finisher. Some small parts are "racked" simply by twisting a thin copper 
 wire around them. The wire, with perhaps 20-50 pieces hanging on it is then handled as a^ 
 "rack". During plating, the part of the rack that makes electrical contact with the part being^ 
 plated is also plated, so after several cycles, these contacts have a lot of metal buildup.The 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 6 
 
racks are then sent through a stripping solution that removes the excess metal, or the plater 
 physically removes the excess metal using pliers or a hammer. Chemical rack strippers are 
 usually strong solutions of cyanide or acid and can be difficult to waste treat. Non-cyanide 
 and regenerative strippers are available for some processes, but are expensive to use or 
 strip very slowly. 
 
 Ill Metal Finishing Process Details 
 
 0 
 
 AUTOMATED RACK PLATING LINE FOR PRINTED WIRING BOARDS 
 
 AUTOMATED RACK PLATING 
 
 Rack plating lines can be automated, using programmable hoists and process controllers. 
 Automated lines yield better product uniformity, provide higher production rates, and 
 generate less waste due to the ability to program and reproduce adequate processing, 
 draining, and rinsing times for the racks. 
 
 Ill Metal finishing Process Details 
 
 Door 
 
 Small Plating Barrels 
 
 Drive Motor 
 
 Dangler 
 
 Door 
 
 B. BARREL PLATING METHOD 
 
 Barrel plating is the most efficient and least costly method. Plating barrels of varied designs 
 are purchased from manufacturers of such products. The basic barrel consists of a 
 hexagonal cylinder, closed at both ends, with perforated walls made of polypropylene. A 
 "door" that is held in place with plastic coated clips, is installed in one wall of the 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 P 3.CS 7 
 
barrel to allow entry and exit of the load. Electrical contact between the saddle on the tank 
 and the parts inside the barrel is made by a copper or bronze rod attached to the barrel that 
 sits in the electrified saddle. The rod has a cable attached, and this cable is routed inside 
 the plating barrel through the end of the barrel. Sometimes two cables are used, one m 
 entering each end of the barrel. The barrel has a hole in the center that allows for the cabi? 
 to enter. The end of the cable, inside the barrel, has a stainless steel ball attached, called a 
 "dangler" This dangler makes contact with the parts inside the barrel by gravity. There are 
 other methods of making electrical contact inside the barrel, including rods and button 
 contacts, but the dangler is the most commonly used method. Parts to be plated are 
 scooped or shoveled into the barrel. The load is often weighed to make certain that the 
 parts are uniformly plated. As a general rule, the barrel is never filled beyond 1/2 the total 
 volume inside. As plating proceeds, a motor mounted either on the plating tank or on the 
 barrel turns the barrel at 3-5 rpm, through either a drive belt or a set of gears mounted on 
 the barrel. If the barrel was not rotated during plating, the top of the load would be plated 
 and the bottom part would remain bare. 
 
 Ill Melal Finishing Process Details 
 
 +1 
 
 Cu 
 
 
 Manually Operated Barrel Plating Line 
 
 Manually Operated Hoist 
 Plating Barrel ______ 
 
 Barrels In Process Tank(s) 
 
 Plating Lines. 
 
 Barrel Plating can be performed on a manually operated plating line as illustrated above. 
 
 The barrel is loaded and transferred from one process tank to the next by a worker using an 
 electric hoist. The worker must take great care to keep the barrel in each process tank for 
 only the required amount of time, so that each work load matches another in quality. 
 Workers must also make certain that each barrel is drained as completely as possible after 
 each process to reduce waste. The plating line should be designed to prevent drippage of 
 process solution from draining to the plant floor. For economy, most barrel plating lines 
 utilize lined and unlined steel tanks, which are prone to corrosion from the outside (as seen 
 in the photo). If not properly maintained, this leads to tank perforation and costly process 
 solution loss. 
 
 * 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 8 
 
Ill Metal Finishing Process Details cu*' o — «cu» 
 
 Automated Oblique Barrel Plating Line 
 
 Plating Barrel 
 
 III Metal Finishin g Process De tails cu*' o — * cu° 
 
 Automated Horizontal Plating Line 
 Programmable Hoist 
 Plating Line_ 
 
 AUTOMATED BARREL PLATING 
 
 The barrel plating operation can be automated by the addition of a programmable hoist to 
 move the barrels and keep track of process times. The newest facilities also incorporate 
 process controllers and even analyzers to automate the process operating conditions and 
 solution chemistries. The programmable hoist line utilizes horizontally oriented barrels that 
 are difficult to automate for loading/unloading. The oblique barrel plating machine shown 
 above, allows for automated loading/unloading because the top of the plating barrel is open. 
 The machine unloads by tilting the barrel upside-down. The oblique plating machine utilizes 
 a return type conveyor to move the barrel from one station to the next. The barrel is lifted 
 (shown in upper right corner) over the tank walls during transfer. In both types of plating 
 machines, the plating thickness obtained is determined by the residence time in the plating 
 tank. In the case of the oblique plater, residence is determined by the size of the plating 
 tank, since the barrel must stay in the tank while the machine indexes (moves the barrel 
 from one place to the next). For this reason, oblique plating machines have very large 
 capacity plating tanks (some machines have 10,000 gallon plating tanks). This results in 
 high operating costs. The barrel in a horizontal plating machine stays in place, reducing 
 solution volume and operating costs. The oblique plater, however, has the advantage of 
 higher productivity. 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Pace 9 
 
Ill M elol Finishing Process Details cu* 
 
 Continuous Strip Plating Schematic 
 
 
 C. CONTINUOUS PLATING METHODS 
 1. STRIP PLATING METHOD 
 
 This method of plating is highly efficient and competes effectively against all other methods, 
 when the parts are small, uniform, simple geometry, and amenable to being stamped from a 
 thin strip of metal, or when parts are small and must be "selectively" plated (plated only in 
 specific areas). This method is used to electrogalvanize (zinc plate) steel strip that is used 
 to stamp automobile bodies and to plate brass or copper strip for stamping electrical ^ 
 connectors for telecommunications. In this method of plating, the parts to be plated consi^^ 
 of long strips of metal that is rolled up into a coil. The coill is mounted on the equipment and 
 the strip goes through a sequence of rollers directing it through various processing tanks, 
 including the plating tank. The metal strip may partially dip into the plating tank, or be 
 completely immersed. The strip may also travel through the plating line in vertical or 
 horizontal orientation. Electrical contact is made either through metal brushes, rollers, or by 
 a principle called "Bipolarity" (electromagnetically induced polarity), which does not actually 
 contact the strip. The strip may travel at speeds ranging from 50 to 1000 or more feet per 
 minute. The strip travels through the same process sequence as for regular plating (clean, 
 rinse, acid, rinse etc.). At the other end of the continuous strip plating line, a second wheel 
 takes up the processed strip. Continuous strip plating equipment is typically automated, 
 except for process chemistry, and is very expensive to purchase, install and operate. The 
 process must be very carefully monitored, or a large amount of waste (reject) material is 
 produced in a very short period of time. This is especially important for continuous plating of 
 precious metals such as gold, or silver. 
 
 ^ 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 10 
 
IllMelalFinish ing Piocms Details cu*' ^ 
 
 ^ Continuous Reel to Reel Plating 
 
 III Melal Finishing Process Details 
 
 Continuous Reel to Reel Plating 
 
 Lead Frame 
 
 Anode 
 
 Electrical Contact 
 
 Recirculating Pump 
 
 Anode 
 
 2CX)-300 Feet Per Minute 
 
 pe lOO's of Feet 
 
 Long) 
 
 Solution Flows 
 Out Of The Slots 
 In The Cell Walls 
 Continuously 
 
 Mask 
 
 Plating Cell 
 
 2. REEL TO REEL PLATING 
 
 This method of plating is similar in principle to strip plating, but this type of plating is usually 
 on a much smaller scale. The tanks for reel to reel plating may only hold a gallon or a few 
 gallons of plating solution. Below the plating cell is a sump tank that holds much more 
 plating solution than the plating cell. The plating solution in the plating cell is continuously 
 replenished via a recirculating pump. Reel to reel plating is commonly performed on 
 electrical contacts for the telephone and computer industry. It is a far more efficient way to 
 plate delicate parts than barrel plating. 
 
 
 ILL Metal Finishing Process I>etails 
 Hardware 
 
 HEATING 
 
 COIL 
 
 AIR 
 
 RECTIFIER 
 
 i _ 
 
 .II 
 
 Ni - 2el 
 
 T" 
 
 DUCTWORK 
 
 PLATING TANK / FILTER 
 
 / AGITATION 
 
 i EXHAUST 
 I STACK 
 
 ; RECIRCULATION 
 TANK 
 
 BLOWDOWN 
 TO WASTE TREAT 
 
 HARDWARE 
 
 The hardware required to perform plating is typically purchased from a company that 
 specializes in producing this equipment, although some platers produce their own hardware. 
 Let’s take a closer look at the hardware used for plating; 
 
 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 11 
 
1. TANK 
 
 The plating tank must resist chemical attack from the plating solution. Tanks containing 
 cyanide plating solutions are often made of bare steel. Tanks for other plating solutions 
 are typically made of steel with PVC lining, polypropylene, polyvinyl chloride, or 
 polyethylene. Plating tanks should not have any wall perforations below the liquid line,^^ 
 prevent accidental discharge of contents. Whenever possible, a tank should be made 
 from non corrodible materials such as polypropylene, polyethylene, Kynar, PVC,or 
 fiberglass. If the tank must be metal, it should be made from stainless steel or lined 
 stainless steel. 
 
 A "rack" plating tank typically has three copper bus bars mounted on top of the tank. 
 
 One bus is in the center and is used to hang the parts in the plating solution. The other 
 two bus bars are located near the walls of the tank, and are used to hang anodes or 
 "baskets" for anodes. 
 
 A barrel plating tank has the same anode bus, but there is no center bus. Instead, the 
 tank typically has four "saddles" made of copper or bronze, mounter to the lips of the 
 tank, so that the barrel contact rods can sit firmly in the saddles. At least one of the four 
 saddles has a cable, or copper bus attached to it for contact with the rectifier. 
 
 Il l Metal Finishing Process De tails c.*' i — • cu” 
 
 RECTIFIERS 
 
 III Metal finishing Process De tails cu*' ® — • cu” 
 
 RECTIFIED 
 
 BANK OF AIR COOLED RECTIFIERS LOCATED ABOVE PROCESS TANKS 
 
 2. RECTIFIER 
 
 The rectifier for plating converts the AC current to DC. The rectifier is typically installed 
 near the plating tank, but may be located in a separate room (in which case a remote 
 control is installed near the tank). In either case, cable or bus bar is used to connect from 
 the positive terminal of the rectifier to the anode bus bar on the tank. The negative 
 terminal of the rectifier is connected by cables or copper bus to the saddle of barrel 
 plating tanks or to the cathode bus of rack tanks. Rectifiers generate heat as a 
 by-product. This heat must be removed by using either a fan (air cooled) or by circulating, 
 cooling water through the rectifier (water cooled). The water used to cool the rectifiers 
 can be routed to other plating or processing operations such as rinsing. 
 
 ^ 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 12 
 
Ill Metfll finishing Process Detaiis cu' » — • cu» 
 
 TYPICAL FILTRATION EQUIPMENT 
 
 3. FILTER 
 
 Some plating solutions require continuous filtration, while others do not. A general rule is 
 that alkaline solutions can usually operate satisfactorily without a filter, while acidic 
 solutions need filtration to avoid particulates suspended in the solution from being 
 incorporated into the coating, yielding "roughness". Use of filters, even on tanks where it 
 is not mandatory, almost always reduces rejects. While the filter shown in the slide is 
 located outside the tank, it is recommended practice to locate the filter inside then tank 
 whenever possible. If located outside, a containment dike or containment tank should be 
 used, as there is spillage of process solution during servicing of the filter (replacement of 
 filter elements or media). 
 
 Newer filters utilize re-usable media to avoid the need for disposing of spent filtration 
 materials. 
 
 Ill Meld finishing Piocess De lais cj 
 
 TYPICAL ELECTRIC HEATERS 
 
 4. HEATING EQUIPMENT 
 
 Many plating processes need to be operated at elevated temperatures, in order for the 
 process to deliver the best performing deposit. Raising the temperature of the process 
 can be performed by inserting a heating coil into the process solution and introducing 
 steam into the coil. The most common alternate method of heating the process solution 
 is to use electric immersion heaters. 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 13 
 
5. AGITATION 
 
 Most plating processes require some form of solution agitation to deliver the brightest, 
 densest, most uniform deposit, and to plate at higher current densities without "burning". 
 A common method of agitation is to move the cathode rod back and forth in the solution 
 using a motor attached to the cathode rod. This is called cathode rod agitation. A second 
 common method is to install an air sparger in the bottom of the plating tank and use low 
 pressure air bubbles to perform the agitation. A less common technique is to use a prop 
 mixer. Plating tanks for barrel plating are not agitated because the rotation of the 
 barrel provides sufficient solution movement. 
 
 Ill Metal Finishing Process Details 
 
 Exhaust 
 
 Ventilation of a Plating Tank 
 
 Water Wash Scrubber 
 
 Mesh Pad Demister 
 
 Exterior Wall of Bldg. 
 
 Plating Tank Hood 
 
 ! Plating Tank 
 
 6. VENTILATION SYSTEM 
 
 Process solutions that emit mists or fumes during storage and use require a ventilation 
 system to capture the offending emissions and emit them outside the process building 
 (for worker safety and to protect equipment from excessive corrosion). If the emissions 
 contain air pollutants that must be controlled, the ventilation system will include a 
 scrubber or demisting system. Scrubbers and demisting systems use water sprays, an^ 
 therefore generate a contaminated wastewater that must either be recycled back to tt^ 
 process or waste treated. Regulations under the Clean Air Act on solvent and (pending) 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 14 
 
chromium emissions cause the metal finishing industry to install more equipment for 
 removal of pollutants from ventilation systems. 
 
 Plating and processing solutions that typically require ventilation systems and scrubbing 
 equipment are: 
 
 Processes Requiring Ventiiation/Scrubbing: 
 
 Ventilation 
 
 Scrubbing 
 
 Chromium Plating (Cr'^®) 
 
 X 
 
 X 
 
 Nickel Plating (Air Agitation) 
 
 X 
 
 
 Woods Nickel 
 
 X 
 
 X 
 
 Hydrochloric Acid 
 
 X 
 
 X 
 
 Nitric Acid 
 
 X 
 
 X 
 
 Hot Cleaners 
 
 X 
 
 
 Electrocleaners 
 
 X 
 
 X 
 
 Electroless Nickel 
 
 X 
 
 
 m Metal Finishing Process Details 
 
 Basic Plating Mechanism 
 
 THE PLATING SOLUTION 
 
 The plating solution normally contains water and a number of ingredients that determine 
 if the coating produced is dense, bright, hard, a certain color, or a number of other 
 desirable properties that can be obtained through chemistry. It also contains an ingredient 
 that forms ions of the metal to be plated when added to water. For example, one 
 ingredient in a watts nickel plating solution is nickel sulfate. When nickel sulfate is added 
 to water, it dissolves and forms nickel ions and sulfate ions, just like when you add salt 
 to water, it dissolves form sodium and chloride ions. The dissolved nickel ions can be 
 converted to nickel metal by passing a direct current through the plating solution using 
 the rectifier (which converts AC current to DC), the anode is the electrode with positive 
 polarity, and the part we want to electroplate is the electrode with negative polarity. The 
 conversion of the nickel ions to nickel metal will occur on the surface of the negative 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 15 
 
electrode, where excess electrons (which make the electrode negatively charged) 
 
 "reduce" the nickel from ions to metal. While nickel ions are converted to metal at the 
 cathode (negative electrode), at the anode, nickel metal is converted from the metal baa^ 
 to the ions. Ideally, for each nickel atom plated out at the cathode, we will form a new^P 
 ion at the anode to replace the one plated out. This is the case in most plating solutions, 
 but there are some solutions where the anode is not converted to metal ions. In cyanide 
 based solutions, metal is plated from metal ions complexed with cyanide. In cyanide zinc * 
 plating solution, zinc is plated from two complexes, the metal-cyanide complex, and a 
 complex between the zinc and hydroxide (called a zincate complex). Tin is plated from an 
 alkaline stannate complex in the alkaline tin plating solution. 
 
 TYPICAL PLATING SOLUTION CHEMISTRIES 
 
 We will now briefly discuss the ingredients of the most commonly used plating solutions: 
 1. ZINC 
 
 Zinc is the most commonly plated metal, normally applied over ferrous substrates for the 
 purpose of enhancing the corrosion resistance. Zinc can be plated from a number of 
 different chemistries, but the three most common ones are cyanide, alkaline non-cyanide, 
 and acid 
 chloride. 
 
 A. Cyanide Zinc 
 
 The cyanide baths are favored when high thicknesses are required or when parts are to 
 be plated and then deformed. Still widely used, cyanide zinc plating solutions contain: 
 
 
 CYANIDE ZINC SOLUTION (g/L) 
 
 Zinc Cyanide 
 
 15-60 
 
 Sodium Cyanide 
 
 8-45 
 
 Sodium Hydroxide 
 
 74-100 
 
 Organic Brightener 
 
 As required 
 
 pH 
 
 14-1- 
 
 Operating Conditions: 
 
 Temperature: 
 
 70-90 deg F 
 
 Anodes: 
 
 Zinc/Steel baskets 
 
 Current Density: 
 
 10-50 ASF 
 
 Agitation: 
 
 Cathode Rod/none 
 
 Filtration: 
 
 Not required 
 
 Color of Solution: 
 
 Straw colored 
 
 Sometimes has floating oily layer) 
 
 Odor of Solution: 
 
 Aldehyde 
 
 Life 
 
 Many Years 
 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 16 
 
B. Alkaline Non-Cyanide 
 
 These baths can be substituted for cyanide baths without the need for major equipment 
 modifications. The deposits tend to become brittle as the thickness increases and some 
 parts that have been heat treated yield poor adhesion. 
 
 ALKALINE NON CYANIDE ZINC (g/L) 
 
 Zinc Oxide 
 
 8-15 
 
 Sodium Hydroxide 
 
 75-110 
 
 Sodium Carbonate 
 
 0-22 
 
 Additives 
 
 As Required 
 
 pH 
 
 14 + 
 
 Operating Conditions: 
 
 Temperature: 
 
 70-90 deg F 
 
 Anodes: 
 
 Zinc/Steel baskets 
 
 Current Density: 
 
 5-45 ASF 
 
 Agitation: 
 
 Cathode rod/none 
 
 Filtration: 
 
 Not required 
 
 Color of Solution: 
 
 Pale Yellow 
 
 Odor of Solution: 
 
 Sharp odor 
 
 Life: 
 
 Many Years 
 
 C. Acid Chloride 
 
 These baths yield the brightest deposit. The process requires excellent cleaning and 
 corrosion resistant equipment, however, and thick deposits tend to be brittle. 
 
 ACID CHLORIDE ZINC (g/L) 
 
 Zinc Chloride 
 
 30-90 
 
 Potassium Chloride 
 
 100-150 
 
 Ammonium Chloride 
 
 22-38 
 
 Boric Acid 
 
 30-38 
 
 pH 
 
 4.5-6.0 
 
 Operating Conditions: 
 
 
 Temperature: 
 
 70-115 deg F 
 
 Anodes: Zinc/Titanium baskets 
 
 Current Density: 
 
 10-150 
 
 Agitation; 
 
 Air or cathode 
 
 rod 
 
 
 Filtration: 
 
 Required 
 
 Color of Solution: 
 
 Pale yellow 
 
 Odor of Solution: 
 
 None, sharp 
 
 with air 
 
 agitation 
 
 Life: 
 
 Many Years 
 
 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 17 
 
2. CADMIUM 
 
 The vast majority of cadmium plating is performed from the cyanide based chemistry. 
 
 The sulfate chemistry has made small in-roads, but often does not adequately cover heat 
 treated steel parts that have high surface hardness. The sulfate process also requires a|l 
 much higher degree of cleaning, or adhesion becomes marginal. 
 
 A. Cyanide Cadmium Baths 
 
 The cyanide based cadmium plating solution contains: 
 
 CYANIDE CADMIUM SOLUTION (g/t) 
 
 Cadmium Oxide 
 
 
 22-38 
 
 Sodium Cyanide 
 
 
 75-150 
 
 Sodium Carbonate 
 
 
 22-100 
 
 Sodium Hydroxide 
 
 
 15-60 
 
 Brighteners/Additives 
 
 As Required 
 
 pH 
 
 
 14-1- 
 
 0 perati ng Co nditi ons: 
 
 
 Temperature: 
 
 
 70-90 
 
 Anodes: Cadmium/Steel Baskets 
 
 Current Density: 
 
 
 5-90 
 
 Agitation: 
 
 Cathode Rod/none 
 
 Filtration: 
 
 Not Required 
 
 Color of Solution: 
 
 Pale Yellow 
 
 Odor of Solution: 
 
 Aldehyde 
 
 Life: 
 
 Many Years 
 
 Acid sulfate based cadmium plating solution contains: 
 
 ACID CADMIUM SOLUTION {glD 
 
 Cadmium Chloride 
 
 8-10 
 
 Ammonium Sulfate 
 
 75-115 
 
 Ammonium Chloride 10-22 
 
 Brighteners/Additives As Required 
 
 pH 
 
 5-6 
 
 Operating Conditions: 
 
 Temperature: 
 
 70-100 deg F 
 
 Anodes: Cadmium, Titanium baskets 
 
 Current Density: 
 
 2-15 ASF 
 
 Agitation: 
 
 Cathode Rod 
 
 Filtration: 
 
 Required 
 
 Color of Solution: 
 
 Pale Yellow 
 
 Odor of Solution: 
 
 Sharp 
 
 Life 
 
 Many Years 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 18 
 
3. COPPER 
 
 Copper is plated from three popular chemistries, cyanide, acid sulfate, and 
 pyrophosphate. Recently, patented alkaline non cyanide copper plating processes have 
 been developed and marketed by at least three companies, but they are troublesome and 
 expensive to operate. 
 
 A. Cyanide Copper Process 
 
 There are several cyanide copper plating processes, but they can be divided into two 
 basic chemistries; a strike bath and a "plate" or high speed bath. 
 
 The ingredients/operating conditions are: 
 
 CYANIDE COPPER SOLUTIONS (g/L) 
 
 
 Strike Plate 
 
 Copper Cyanide 
 
 10-15 30-60 
 
 Sodium Cyanide 
 
 22-30 60-90 
 
 Sodium Carbonate 
 
 22-100 22-100 
 
 Sodium Hydroxide 
 
 0-10 15-30 
 
 Brlghtener/Additives 
 
 (none) As Required 
 
 pH 
 
 10-10.5 12-14 
 
 Note: Potassium salts are most often used in high 
 
 speed cyanide copper plating solutions, at 
 
 approximately the same concentrations. 
 
 Operating Conditions: 
 
 Temperature: 
 
 140-160 deg F. 
 
 Anodes: Oxygen Free High Conductivity (OFHC) 
 
 Copper 
 
 
 Current Density: 
 
 10-100 ASF 
 
 Agitation: 
 
 Cathode Rod 
 
 Filtration: 
 
 Required 
 
 Color of Solution: 
 
 Pale Yellow 
 
 Odor of Solution: 
 
 Pungent 
 
 Life 
 
 Strike: Years Plate: Many Years 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 I 
 
 Page 19 
 
B. Acid Sulfate Processes 
 
 There are two main acid sulfate chemistries used in electroplating copper. One is termed 
 "conventional" and is often used as an underlayer for plated plastic, or in applications 
 where a high degree of "leveling" (smoothing of scratches) is desired. The second '■ 
 process is called a high-throw bath, used mostly by printed wiring board manufacturers 
 because of the ability to produce uniform thicknesses on the outside of a circuit board 
 and on the inside of tiny holes drilled into the board. 
 
 ACID COPPER PLATINO SOLUTIONS (g/L) 
 
 
 Conventional 
 
 High Throw 
 
 Copper Sulfate 
 
 200-250 
 
 75-100 
 
 Sulfuric Acid 
 
 45-90 
 
 150-300 
 
 Chloride 
 
 40-80 
 
 40-80 ppm 
 
 Brighteners/Additives 
 
 yes yes 
 
 pH 
 
 <1 
 
 <1 
 
 Operating Conditions: 
 Temperature: 
 
 Room 
 
 
 Anodes: Copper containing 0.02-0.06 % phosphorus, bagged 
 
 Plating Current Density: 
 
 20-200 
 
 
 Agitation: 
 
 Air 
 
 
 Filtration: 
 
 Continuous 
 
 
 Color Of Solution: Deep Cobalt Blue 
 
 Odor Of Solutiortilo specific smell, inhaled mist 
 
 may yield 
 
 sharp 
 
 
 
 
 odor/burning of nose 
 
 Life 
 
 Many Years 
 
 
 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 20 
 
PYROPHOSPHATE COPPER SOLUTIONS (g/L) 
 
 Copper Pyrophosphate 
 
 75-90 
 
 Potassium Pyrophosphate 300-350 
 
 Potassium Nitrate 
 
 7.5-12 
 
 Ammonia 
 
 1-4 
 
 Additives 
 
 Variable 
 
 pH 
 
 8-9 
 
 Operating Conditions: 
 Temperature: 
 
 125-135 deg F 
 
 Anodes: 
 
 Oxygen Free High 
 
 Conductivity Copper 
 
 
 Titanium Baskets 
 
 Plating Current Density: 10-90 ASF 
 
 Agitation: 
 
 Air 
 
 Filtration: 
 
 Yes 
 
 Color of Solution: 
 
 Iridescent 
 
 
 blue/purple 
 
 Life 
 
 A Few Years 
 
 C. Pyrophosphate Copper Solutions 
 
 These plating solutions are almost exclusively used by printed circuit board 
 manufacturers. Their major benefits include low copper concentration and the ability to 
 deposit an even thickness over complex geometries, such as the top of a circuit board vs 
 the inside of a drilled hole. 
 
 The majority of these solutions have been replaced with bright throw acid sulfate 
 systems because the pyro baths are much more difficult chemistries to analyze and 
 control. You may find the baths in some job shops as substitutes for cyanide copper 
 strike baths on zinc die castings or for copper striking zincated aluminum. 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 21 
 
4. BRASS PLATING 
 
 Currently, there are no commercially viable processes for plating brass, and alloy of 
 copper and zinc, other than from a cyanide based chemistry. Brass is applied mostly for 
 decorative purposes, wherein it is subsequently stained to yield an "antique" or coloredl^ 
 finish. Brass is also applied to enhance adhesion of rubber to steel. Brass readily 
 tarnishes, so most often it is finished off with a coat of lacquer. 
 
 BRASS PLATING SOLUTION (g/L) 
 
 Copper Cyanide 
 
 30-60 
 
 Zinc Cyanide 
 
 8-15 
 
 Sodium Cyanide 
 
 15-30 
 
 Sodium Carbonate 
 
 22-100 
 
 pH 
 
 10-11.5 
 
 Operating Conditions: 
 
 Temperature: 
 
 125-135 deg F 
 
 Anodes: Brass of same alloy composition as plated 
 
 Current Density; 
 
 5-15 ASF 
 
 Agitation: 
 
 Cathode Rod 
 
 Filtration: 
 
 Yes 
 
 Color of Solution: 
 
 Pale yellow 
 
 Odor of Solution: 
 
 No specific 
 
 Life 
 
 Many Years 
 
 BRONZE PLATING SOLUTION (g/L) 
 
 Copper Cyanide 
 
 35 
 
 Potassium Cyanide 
 
 80 
 
 Potassium Stannate 
 
 42 
 
 Potassium Hydroxide 12 
 
 Sodium Potassium Tartrate 45 
 
 pH 
 
 12 + 
 
 Operating Conditions; 
 
 Temperature: 
 
 150-160 deg F 
 
 Anodes; Copper/carburized Steel, graphite, 
 
 
 or stainless steel 
 
 Current Density: 
 
 20-100 ASF 
 
 Agitation: 
 
 Cathode Rod 
 
 Filtration: 
 
 Yes 
 
 Color of Solution: 
 
 Pale yellow 
 
 Odor of Solution: 
 
 Pungent 
 
 Life 
 
 Many Years 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 22 
 
5. BRONZE 
 
 Bronze (80% Copper 20% Tin) can only be plated from a cyanide based chemistry. The 
 plating equipment is identical to that for copper, or brass plating. 
 
 6. ZINC ALLOY 
 
 Alloys of zinc have been the major focus for a good substitute for cadmium plating. If an 
 alloy of zinc contains a small amount of a more noble metal, such as nickel, tin, cobalt, or 
 iron, the zinc retains its cathodic relationship with steel, but the alloying metal reduces 
 the activity of the coating so that it corrodes sacrificially at a slower rate, thereby 
 enhancing corrosion protection over plain zinc. There are numerous zinc alloy processes 
 being touted as the best cadmium alternative, including zinc-nickel, zinc-cobalt, zinc-tin, 
 and zinc-iron. Of these, zinc-nickel appears to be a favorite at this time while some 
 zinc-cobalt installations have been made. The others are either too expensive or do not 
 produce a pleasing enough appearance to be applicable for anything other than as a paint 
 undercoat for automobile body panels. The equipment for plating zinc alloys is identical to 
 that used for nickel plating (see below). 
 
 A. Zinc-Nickel 
 
 Zinc-Nickel alloys can be plated from both alkaline and acidic chemistries, with the 
 alkaline process the most often favored. 
 
 Alkaline Zinc Nickel 
 
 ALKALINE ZINC-NICKEL SOLUTION (g/L) 
 
 Zinc 
 
 8-15 
 
 Sodium Hydroxide 
 
 90-130 
 
 Nickel 
 
 1-1.5 
 
 Additives 
 
 As required 
 
 pH 
 
 14 + 
 
 Operating Conditions; 
 
 Temperature: 
 
 70-90 deg F 
 
 Anodes; Zinc and Steel 
 
 Current Density: 
 
 10-45 ASF 
 
 Agitation: 
 
 Cathode Rod 
 
 Filtration: 
 
 Yes 
 
 Color of Solution: 
 
 Yellow 
 
 Odor of Solution: 
 
 No specific 
 
 Life 
 
 No Data (New Process) 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 23 
 
B. Zinc Cobalt 
 
 ACID ZINC COBALT SOLUTION (g/L) 
 
 Zinc chloride 
 
 75-90 
 
 Potassium Chloride 
 
 200-250 
 
 Cobalt 
 
 2-3.5 
 
 Boric Acid 
 
 22-30 
 
 pH 
 
 5-6 
 
 Operating Conditions: 
 
 Temperature: 
 
 65-95 deg F 
 
 Anodes: Zinc, bags Current 
 
 Density: 
 
 1-40 ASF 
 
 Agitation: 
 
 Air 
 
 Filtration: 
 
 Yes 
 
 Color of Solution: 
 
 Pale with slight purple 
 
 Odor of Solution: 
 
 No specific 
 
 Life 
 
 No Data (New Process) 
 
 7. NICKEL 
 
 Nickel is most often plated from the "Watts" chemistry, although there are numerous 
 other formulations, including a specialized "Woods Nickel Strike" that is used to obtain 
 adhesion on stainless steels. The watts bath is used to obtain bright or semi-bright ^ 
 deposits for decorative applications. In decorative applications where deposit appearanfP 
 and corrosion resistance are highly important, as on the exterior of an automobile, two or 
 more layers of nickel from watts baths are applied. The most common such layered nickel 
 plating is referred to as "duplex nickel" which consists of two layers of nickel. The first 
 layer is called semi-bright nickel, containing no sulfur bearing brighteners and the second 
 layer is a fully bright nickel deposit containing a controlled amount of sulfur bearing 
 brightener. 
 
 The duplex nickel is normally topped off with a thin coating of chromium plating. The 
 bright nickel layer corrodes in favor of the semi bright, protecting it galvanically and 
 delaying the onset of corrosion of the base metal. 
 
 Another often used nickel plating formulation is the sulfamate based chemistry. It is used 
 in electroforming or other applications where a nickel deposit containing no or low 
 internal stress is desired. 
 
 Nickel is also used to plate "composite" deposits, where the plated nickel contains finely 
 dispersed diamond dust or other abrasives such as silicon carbide. Such composite 
 coatings are used to create long lasting cutting tools. 
 
 A. Watts Nickel 
 
 The watts nickel plating chemistry can contain a variety of additives to control pitting, 
 yield "levelling", and produce brightness from a medium (semi-bright) to a full mirror ^ 
 bright deposit. Additives are normally patented products sold by suppliers along with t" 
 plating chemicals. 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 24 
 
WATTS NICKEL SOLUTION (g/L) 
 
 Nickel Sulfate 
 
 225>350 
 
 Nickel Chloride 
 
 30-90 
 
 Boric Acid 
 
 30-45 
 
 Additives 
 
 As Required 
 
 pH 
 
 3-5 
 
 Operating Conditions: 
 
 Temperature: 
 
 125-135 deg F 
 
 Anodes: 
 
 Nickel or Nickel containing 
 
 0.02 % Sulfur or others. Bagged 
 
 Current Density: 
 
 25-100 ASF 
 
 Agitation: 
 
 Cathode Rod or Air 
 
 Filtration: 
 
 Yes 
 
 Color of Solution: 
 
 Deep Green 
 
 Odor of Solution: 
 
 No specific 
 
 Life 
 
 Many Years 
 
 B. Wood's Nickel Strike 
 
 This bath is purposely designed to generate high volumes of hydrogen gas, while 
 depositing only a thin layer of nickel, even at the highest current densities. The major use 
 is to obtain adherent thin nickel deposits that can then be plated with other metals. 
 
 WOODS NICKEL STRIKE (g/L) 
 
 Nickel Chloride 
 
 225 
 
 Hydrochloric Acid 
 
 100-200 ml/L 
 
 pH 
 
 <.1 
 
 Operating Conditions: 
 
 Temperature: 
 
 70-90 deg F 
 
 Anodes: 
 
 Nickel 
 
 Current Density: 
 
 100-300 ASF 
 
 Agitation: 
 
 None 
 
 Filtration: 
 
 None 
 
 Color of Solution: 
 
 Dark Green 
 
 Odor of Solution: 
 
 Sharp Hydrochloric Fumes 
 
 Life 
 
 Years 
 
 C. Sulfamate Nickel 
 
 The sulfamate nickel chemistry is used mainly for electroforming purposes, although 
 some electronic applications requiring a low stress nickel underplate for gold overplates 
 also use this bath. The equipment for sulfamate plating is identical to that used for watts 
 baths, with the exception that the sulfamate process will typically have a purification 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 25 
 
compartment attached to the tank, incorporated into the tank, or alongside the tank. The 
 purification compartment is about 1/5 the size of the plating tank and the solution is 
 
 SULFAMATE NICKEL SOLUTION (g/L) 
 
 Nickel Sulfamate 
 Magnesium Chloride 
 Boric Acid 
 Additives 
 pH 
 
 As Recommended 
 3-5 
 
 450525 
 
 8-15 
 
 45-55 
 
 Operating Conditions: 
 
 Temperature: 125-135 deg F 
 
 Anodes: Sulfur Depolarized Nickel 
 
 Current Density: 
 Agitation: 
 
 20-140 ASF 
 
 Air 
 
 Yes 
 
 Filtration: 
 
 Color of Solution: 
 Odor of Solution: 
 Life 
 
 Deep Green 
 No specific 
 
 Many Years 
 
 recirculated through the compartment, using the filtration system. In the purification 
 compartment, electrolytic nickel anodes and dummy electrodes plate out metallic 
 contaminants and the polarization occurring at the anodes decomposes some of the 
 sulfamate ions into stress reducing compounds. 
 
 D. Sulfamate Nickel Strike 
 
 An alternate strike solution can be used to activate stainless steel (vs the Woods Nickel 
 Strike). This solution eliminates the hydrochloric acid, which causes a safety and 
 ventilation hazard. 
 
 SULFAMATE NICKEL STRIKE 
 
 Nickel Sulfamate 320g/L 
 Sulfamic Acid 150g/L 
 
 Operating Conditions: 
 
 Temperature: 
 
 Anodes: 
 
 Current Density: 
 
 Agitation: 
 
 Filtration: 
 
 Color of Solution: 
 Odor of Solution: 
 Life: 
 
 50°C 
 
 Electrolytic Nickel 
 
 50ASF 
 
 None 
 
 Yes 
 
 Deep Green 
 No Specific 
 Years 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 26 
 
8. CHROMIUM 
 
 Chromium plating generally falls into two categories; decorative and "hard". Both 
 categories can and are being plated from the same chemistries based on hexavalent 
 chromium, while decorative chromium can also be plated from one of several trivalent 
 chemistry. The terms decorative and hard are confusing and really mean "thin" and 
 "thick". All chromium plates have a hardness in the same range (900-1100 vickers). 
 Decorative chromium is a very thin layer of chromium applied over a substrate that has 
 been bright nickel plated. The appearance of decorative chromium, to a large extent, is 
 due to the appearance of the nickel. The chromium is so thin (3-20 millionths of an inch), 
 that is essentially transparent. Decorative chromium plating equipment is identical to that 
 of hard chromium. An exception is the trivalent decorative chromium, which typically has 
 no exhaust system and requires continuous filtration. 
 
 "Hard" chromium should be called engineering chromium, because it is usually applied 
 when a hard wear resistant metallic coating is required on a part that is subject to 
 abrasive forces during service. A typical example is the chromium applied to hydraulic 
 shafts for heavy equipment, on the piston rings of internal combustion engines, and on 
 the shafts of landing gears of aircraft. A typical chromium plating tank is constructed of 
 steel with a PVC lining. It is equipped with heating elements and an exhaust system to 
 remove the chromic acid fumes from the workers' breathing zone. 
 
 CHROMIUM PLATING SOLUTIONS (HEXAVALENT) 
 
 Chromium Trioxide 225-260 
 Sulfate 2.25-2.6 
 
 Operating Conditions: 
 
 Temperature: 125-135 deg F 
 
 (for hard plating applications, temp, may be at 140 deg.F ) 
 
 Anodes: 
 
 Current Density: 
 
 Agitation: 
 
 Filtration: 
 
 Color of Solution: 
 Odor of Solution: 
 Life: 
 
 Lead 
 
 Decorative 100-150 ASF, 
 
 Hard 150-250 ASF 
 
 None (Hard may use some air agitation) 
 No 
 
 Deep dark red-brown 
 No specific 
 Many Years 
 
 Mixed Catalyst Solutions: 
 
 Chromium Trloxide 
 
 Sulfate 
 
 Fluoride 
 
 30-45 oz/gal 
 .15-.18 oz/gal 
 .13 oz/gal 
 
 Note: fluoride may be present as one or more of a variety of 
 fluoride containing compounds. 
 
 Operating Conditions/Life: Same 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 27 
 
A. Hexavalent Chemistries 
 
 The hexavalent chromium plating chemistries fall into two categories, conventional, and 
 mixed catalyst. The conventional is a simple chemistry that anyone can mix up and use^ 
 The mixed catalyst chemistries are patented processes that have a few advantages, ® 
 including faster plating, less problems caused by current interruption, and fewer problems 
 plating onto passive nickel deposits. They also tend to be more difficult to control and 
 expensive to operate. In hard chromium applications, mixed catalyst baths also tend 
 to etch steel in areas where plating is not intended, making masking more critical. 
 
 B. Trivalent Chemistries 
 
 Trivalent chemistries were developed in response to concerns about the detrimental 
 effects of hexavalent chromium on the environment and workers' health. Hexavalent 
 chromium is a powerful oxidizer that readily attacks human tissues and has been linked in 
 some studies to lung cancer. Trivalent chromium has a much lower toxicity level, is not 
 an oxidizer and has to date not been linked with cancer. Platers have been slow to accept 
 trivalent chromium chemistries as substitutes for hexavalent chemistries because they 
 tend to plate deposits that are noticeably darker or not consistently of the same color. 
 Since trivalent baths are only used for decorative applications, this is a major drawback, 
 but solution manufacturers have made great progress towards solving these problems. A 
 major benefit from trivalent processes is that these baths contain very low concentrations 
 of chromium (about 1/5th as much),and the chromium can be waste treated without a 
 reduction step, so waste treatment and sludge disposal costs are reduced. Equipment 
 generally consist of a rubber or plastic lined steel or plastic tank, an air agitation system, 
 heating and cooling system, and a filtration system. 
 
 Trivalent Chromium Plating Solutions (g/L): 
 
 TC Additive 
 
 400 
 
 (Chromium Cone is 
 
 20 
 
 TC Stabilizer 
 
 8% voi 
 
 TC-SA 
 
 1.2 %vol 
 
 TC Regulator 
 
 1 ml/L 
 
 pH 
 
 3.2 
 
 Operating Conditions: 
 
 Temperature: 
 
 70-90 deg F 
 
 Anodes: 
 
 Graphite (Harshaw) 
 
 (Lead in membrane cell Enthone-OMI) 
 
 Current Density: 
 
 90-200 ASF 
 
 Agitation: 
 
 Air 
 
 Filtration: 
 
 Yes 
 
 Color of Solution: 
 
 Deep blue-Green 
 
 Odor of Solution: 
 
 No specific 
 
 Life: 
 
 Many Years 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 28 
 
9. GOLD 
 
 Gold can be plated from three major chemistries; alkaline cyanide, neutral, and acid. All 
 three chemistries utilize gold from potassium gold cyanide salts. A proprietary gold 
 plating process that does not utilize potassium gold cyanide is on the market, but is 
 expensive to 
 
 operate and limited in alloying capability. Most gold plated is an alloy of gold and some 
 other metal or combination of metals such as nickel, cobalt, copper and silver. Gold can 
 be plated in any commercial "Karat" desired. The neutral and acid gold plating 
 chemistries utilize chelating agents to perform the tasks normally performed by cyanide, 
 control of metallic impurities and alloying elements. While these chelates could cause 
 waste treatment problems, they rarely enter the wastewater treatment system in high 
 concentrations, since most gold plating operations have meticulous recovery systems to 
 use as little rinsewater as possible and recover the plating chemicals. 
 
 A. Alkaline Cyanide Chemistry 
 
 This bath is most often used to apply a thin film of gold over bright nickel in decorative 
 applications such as jewelry. The plating tank is a typical layout with a plastic or lined 
 steel tank, filtration, cathode rod agitation (optional), and heating elements. 
 
 CYANIDE GOLD PLATING SOLUTION (g/L) 
 
 Potassium Gold Cyanide 1-4 
 
 Potassium Cyanide 
 
 1-12 
 
 Potassium Carbonate 22-200 
 
 Additives 
 
 As Required 
 
 pH 
 
 10 
 
 Operating Conditions: 
 
 Temperature: 
 
 125-150 deg F 
 
 Anodes: 
 
 Gold or Stainless Steel or 
 
 
 Platinized Titanium 
 
 Current Density: 
 
 1-35 ASF 
 
 Agitation: 
 
 Cathode Rod 
 
 Filtration: 
 
 Yes 
 
 Color of Solution; 
 
 Dark yellow 
 
 Odor of Solution: 
 
 No specific 
 
 Life: 
 
 Many Years 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 29 
 
B. Neutral Gold Plating Chemistry: 
 
 These solutions are favored for barrel plating applications of high purity gold. 
 
 NEUTRAL GOLD PLATING SOLUTION (g/L) 
 
 Potassium Gold Cyanide 8-12 
 
 Monopotassium Phosphate 75-90 
 
 Potassium Citrate 
 
 60-75 
 
 pH 
 
 6-6.5 
 
 Operating Conditions: 
 
 Temperature: 
 
 125-135 deg F 
 
 Anodes: 
 
 Platinized Titanium 
 
 Current Density: 
 
 1-3 ASF 
 
 Agitation: 
 
 Cathode Rod/Recirc Pump 
 
 Filtration: 
 
 Yes 
 
 Color of Solution: 
 
 Pale yellow/clear 
 
 Odor of Solution: 
 
 No specific 
 
 Life; 
 
 Many Years 
 
 C. Acid Gold Plating 
 
 Acid gold baths can produce a variety of gold deposits, including the hardest, most wea 
 resistant. They are favored for plating of printed circuit board connectors and in the ^ 
 semi-conductor industry. 
 
 ACID GOLD PLATING SOLUTION (g/L) 
 
 Potassium Gold Cyanide 4-8 
 
 Citric Acid 
 
 30-60 
 
 Ammonium Citrate 
 
 30-45 
 
 pH 
 
 3-5 
 
 Operating Conditions: 
 
 Temperature: 
 
 90-140 deg F 
 
 Anodes: 
 
 Platinized Titanium 
 
 
 or Platinized Niobium 
 
 Current Density: 
 
 1-5 ASF 
 
 Agitation: 
 
 Cathode Rod 
 
 Filtration: 
 
 Yes 
 
 Color of Solution: 
 
 Range from clear to purple 
 
 Odor of Solution: 
 
 No specific 
 
 Life: 
 
 Many Years 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 30 
 
SILVER PLATING SOLUTION (g/L) 
 
 Silver Cyanide 
 
 8-30 
 
 Potassium Cyanide 
 
 15-30 
 
 Sodium Carbonate 
 
 22-100 
 
 Potassium Hydroxide 
 
 8-15 
 
 Potassium Nitrate 
 
 0-15 
 
 pH 
 
 12-14 
 
 Operating Conditions: 
 
 Temperature: 
 
 70-90 deg F 
 
 Anodes: 
 
 Silver 
 
 Current Density: 
 
 1-40 ASF 
 
 Agitation: 
 
 Cathode Rod 
 
 Filtration: 
 
 Yes 
 
 Color of Solution: 
 
 Dark Brown/black 
 
 Odor of Solution: 
 
 Organic 
 
 Life: 
 
 Many Years 
 
 10. SILVER 
 
 While non cyanide silver plating chemistries based on sulfites or succinimides have been 
 available for some time, most all silver plating is presently being performed in the cyanide 
 chemistry. The non-cyanide baths are far more expensive to install and operate and 
 can not tolerate contamination to the same degree as the cyanide process. The plating 
 equipment is typically a lined steel or plastic tank equipped with a filter and cathode rod 
 agitation. Silver can also be barrel plated. 
 
 11. TIN 
 
 Tin can be plated from more than four major chemistries; the alkaline stannate process, 
 the fluoborate, the proprietary "halogen" and sulfonate processes, and the sulfuric acid 
 based process. The alkaline stannate, flouborate, and sulfate chemistries are most 
 often encountered in job shops. The alkaline stannate process typically consists of a 
 heated steel tank, while the sulfuric acid based process uses a plastic or pvc lined steel 
 tank and has filtration. The alkaline process produces a mat, pure tin deposit that has 
 excellent solderability, while the sulfate process produces mat or bright deposits with 
 lesser or marginal solderability but superior appearance. The alkaline process is a bit more 
 difficult to operate than the sulfate process. The alkaline bath is favored for barrel plating 
 applications, although the flouborate bath can also be used. 
 
 Compositions (oz/gal) and operating conditions are: 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 31 
 
Alkaline Stannate (g/L): 
 
 
 
 Rack 
 
 Barrel 
 
 Potassium Stannate 
 
 100 
 
 200 
 
 Potassium Hydroxide 
 
 15 
 
 22 
 
 Potassium Carbonate 
 
 22-100 
 
 22-100 
 
 Additives: 
 
 None 
 
 None 
 
 pH 
 
 >14 
 
 >14 
 
 Note: 2 to 4 g/L of cyanide is sometimes 
 
 
 added to reduce the effects of metallic contaminants. 
 
 Operating Conditions: 
 
 
 
 Temperature: 
 
 150-180 deg F 
 
 Anodes: 
 
 Tin 
 
 
 Current Density: 
 
 1-100 ASF 
 
 
 Agitation: 
 
 Cathode Rod 
 
 
 Filtration: 
 
 No 
 
 
 Color of Solution: 
 
 Pale yellow or white/ciear 
 
 Odor of Solution: 
 
 No specific 
 
 
 Life: 
 
 Many Years 
 
 
 Fluoborate Tin Solutions (rack/barrel plating) (g/L) 
 
 Tin (from concentrate) 
 
 30-45 
 
 Fluoboric Acid 
 
 200-250 
 
 Boric Acid 
 
 22-40 
 
 Additives 
 
 As Recommended, but required 
 
 pH 
 
 <.1 
 
 Operating Conditions: 
 
 Temperature: 
 
 90-120 deg F 
 
 Anodes: 
 
 Tin 
 
 Current Density: 
 
 1-80 ASF 
 
 Agitation: 
 
 Cathode Rod 
 
 Filtration: 
 
 Yes 
 
 Color of Solution; 
 
 Pale yellow 
 
 Odor of Solution: 
 
 No specific 
 
 Life: 
 
 Many Years 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 3 2 
 
Acid Sulfate Tin Solutions (g/L) 
 
 Stannous Sulfate 
 
 15-45 
 
 Sulfuric Acid 
 
 7.5-22 
 
 Additives 
 
 As Recommended, but required 
 
 pH 
 
 <1 
 
 Operating Conditions: 
 
 Temperature: 
 
 55-85 deg F 
 
 Anodes: 
 
 Tin 
 
 Current Density: 
 
 1-25 ASF 
 
 Agitation: 
 
 Cathode Rod 
 
 Filtration: 
 
 Yes 
 
 Color of Solution: 
 
 Pale yellow/clear 
 
 Odor of Solution: 
 
 Sweet 
 
 Life: 
 
 Many Years 
 
 12. TIN-LEAD 
 
 Tin-Lead is applied to electronic components that require high solderability. The plating 
 hardware is a typical plating setup with continuous filtration optional. There are two 
 basic chemistries the alloy is plated from; the fluoboric and the (proprietary) sulfonic 
 acid based chemistries. These baths are most commonly found in printed circuit board 
 manufacturing shops and job shops specializing in plating for electronics. The electronics 
 industry uses a "high throw" formulation to allow for plating inside drilled holes. Others 
 use a conventional bath that yield the best solderability. The fluoborate bath is made by 
 mixing liquid fluoborate concentrates with water. 
 
 Tin-Lead (Solder) Solutions (g/L) 
 
 
 
 Conventional 
 
 High Throw 
 
 Tin (from concentrate) 
 
 52-60 
 
 12-20 
 
 Lead (from concentrate) 
 
 22-30 
 
 8-14 
 
 Fluoboric Acid 
 
 100-150 
 
 350-500 
 
 Boric Acid 
 
 22-40 
 
 22-40 
 
 pH 
 
 <.1 
 
 <.1 
 
 Temperature: 
 
 70-90 deg F 
 
 
 Anodes: 
 
 Lead-Tin Alloy 
 
 Current Density: 
 
 15-25 ASF 
 
 
 Agitation: 
 
 Cathode Rod 
 
 
 Filtration: 
 
 Yes 
 
 
 Color of Solution: 
 
 Pale yellow 
 
 
 Odor of Solution: 
 
 Sweet 
 
 
 Life: 
 
 Many Years 
 
 
 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 33 
 
ELECTROLESS PLATING PROCESSES 
 
 One major drawback to electroplating is the non uniform coating produced, because 
 electric current tends to concentrate on sharp edges, corners and points. ^ 
 
 Electroless plating processes are used when it is necessary to obtain a very uniform ™ 
 
 coating on complex geometries, because these processes do not depend upon electricity 
 delivered from a rectifier. As the name implies, the coating is produced without an 
 outside source of current. The reducing electrons are chemically provided. 
 
 Some electroless deposits are also more corrosion resistant than their electroplated 
 counterparts. The following are two of the most often applied electroless processes: 
 
 A. ELECTROLESS NICKEL 
 
 Electroless nickel is applied to numerous complex electronic and industrial components 
 for the high degree of wear resistance and corrosion protection. An example is the sliding 
 plates that "mold" the hamburger patties served in fast food restaurants. Two plates 
 slide against each other forming the cavity that is used to "injection mold" the patty. The 
 plates slide against each other at lighting fast speeds. Electroless nickel is also used in 
 the plating of plastics, to provide the first metallic layer on the plastic to yield 
 conductivity 
 
 for subsequent deposits. 
 
 The electroless plating process normally consists of two plating tanks and a nitric acid 
 storage tank. Each plating tank contains heating elements, an air sparger, and a 
 recirculating filter. The solution will eventually deposit nickel on everything it contacts, so 
 periodically the tank walls and associated equipment must be stripped with nitric acid 
 (thus the nitric storage tank). The plating solution has a finite life (8-14 "turnovers"), 
 after which, it must be waste treated or disposed of through a commercial disposal firm. 
 The electroless nickel plating solution contains strong chelating agents that interfere with 
 a conventional wastewater treatment system, so they must be treated separately using 
 electrowinning, proprietary treatment methods, or special chemical treatments. The 
 rinsewater from electroless nickel operations is usually segregated and treated separate 
 from other rinsewater. 
 
 Nickel-Phosphorus Electroless Solutions (g/L) 
 
 Nickel Sulfate: 
 
 21 
 
 11.8 
 
 Acetic Acid 
 
 9.3 
 
 
 Lactic Acid 
 
 27 
 
 
 Molybdic Acid 
 
 
 .009 
 
 Propionic Acid 
 
 2.2 
 
 
 Lead Acetate 
 
 .001 
 
 
 1,3 Diisopropyl Thiourea 
 
 
 .004 
 
 Sodium Hypophosphite 
 
 24 
 
 22.3 
 
 pH 
 
 4.6 
 
 5.5 
 
 Temperature 
 
 95®C 
 
 95°C 
 
 Life: 
 
 Weeks/Months 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 34 
 
Electroless nickel is typically plated from one of two basic chemistries, yielding either a 
 nickel-phosphorus alloy (most common) or a nickel-boron alloy. Each alloy can be plated 
 from a number of different solutions to yield varying alloy compositions. Shown are 
 typical formulations: 
 
 Nickel-Boron Electroless Solution (g/L) 
 
 Nickel Chloride 
 
 30 
 
 Sodium Hydroxide 
 
 40 
 
 Ethylene Diamine 
 
 86ml/L 
 
 Sodium Borohydride 
 
 0.6 
 
 Thallium Nitrate 
 
 0.007 
 
 Sodium Gluconate 
 
 15 
 
 Diethyl amine Borane 
 
 1.0 
 
 Lead Acetate 
 
 0.02 
 
 pH 
 
 13-14 
 
 Temperature 
 
 90 deg C 
 
 Life: Weeks/Months 
 
 B. ELECTROLESS COPPER 
 
 The major use for electroless copper is in the manufacture of printed wiring boards. The 
 electroless copper is used to apply a thin coating of copper over the top-side and into the 
 drilled holes of the boards. The drilled holes are initially non-metallic, since the boards are 
 made of epoxy-fiberglass. With the electroless copper the holes become conductive for 
 further plating. 
 
 Equipment for electroless copper plating usually consists of a polypropylene or PVC 
 plastic tank and filter. Some baths operate at room temperature, so heating is not 
 required, other require heating. The rinsewater and spent electroless copper often contain 
 chelating or complexing agents, so waste treatment becomes difficult. 
 
 A typical composition (g/L) electroless copper solution is. 
 
 Electroless Copper Solutions (g/L) 
 
 Copper Sulfate 
 
 13.8 
 
 5 
 
 Rochelle salts 
 
 69,2 
 
 25 
 
 Sodium Hydroxide 
 
 20 
 
 7 
 
 MBT 
 
 .012 
 
 
 Formaldehyde 
 
 38ml/L 
 
 lOml/L 
 
 Temperature 
 
 50 deg C 
 
 25 deg C 
 
 Life: 
 
 Weeks/Months 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 35 
 
C. OTHERS 
 
 There are numerous other electroless plating solutions in the literature, although they are 
 rarely used. The following solutions may be encountered: 
 
 ELECTROLESS COBALT (g/L) 
 
 Cobalt Sulfate 30 
 
 Ammonium Chloride 84 
 
 Sodium Hypophosphite 20 
 pH 10 
 
 Temperature 95 deg C 
 
 Life: Weeks/Months 
 
 ELECTROLESS SILVER (g/L) 
 
 Silver Cyanide 
 
 1.34 
 
 Sodium Cyanide 
 
 1.49 
 
 Sodium Hydroxide 
 
 0,75 
 
 Dimethyl Amine Borane 
 
 2 
 
 Temperature 
 
 55 deg C 
 
 Life: Weeks/Months 
 
 ELECTROLESS GOLD (g/L) 
 
 
 Potassium Gold Cyanide 
 
 5.8 
 
 Potassium Cyanide 
 
 13 
 
 Potassium Hydroxide 
 
 11 
 
 Potassium Borohydride 
 
 21.6 
 
 Temperature 
 
 75 deg C 
 
 Life: 
 
 Days 
 
 TYPICAL POST PLATING OPERATIONS-CHROMATING 
 
 After plating, parts are often further treated in various chemical solutions to enhance the 
 appearance or corrosion/tarnish resistance of the plated coating. Examples of such 
 operations include chromate films on zinc, cadmium, and copper plates, and stains 
 produced on copper or copper alloy deposits. Application of lacquers, waxes, and other 
 organic topcoats are also popular post plating methods for improving shelf and service life 
 of parts. Chromate "conversion" coatings are so popular, that almost every zinc and 
 cadmium plating line has chromating tanks and rinses built into it and most all zinc and 
 cadmium plated parts have some form of chromate film on top of the metal deposit. W 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 36 
 
Chromating 
 
 A chromate is a very thin complex film created by "converting" a small amount of the top 
 surface of the plated metal into the film, thus the term conversion coating. 
 
 The chromate film is formed by immersing the plated deposit into an acidic solution 
 containing a variety of chemicals depending upon the color and corrosion resistance we 
 want to obtain. If, for example, we want the zinc to turn bright, reflective, and with a 
 hint of blue (typically called a blue-bright dip), our solution will contain nitric acid, and 
 potassium ferricyanide, along with some trivalent chromium compounds. If we want a 
 yellow iridescence, hexavalent chromium, in the form of sodium dichromate may be 
 added. If we want olive drab green, even more dichromate along with sulfates may be 
 added. If we want a black coating, a small amount of silver nitrate is added (finely 
 divided silver particles create the black color). 
 
 In each case, the mechanism for forming the chromate film is the same: The plated metal 
 is attacked by the acid in the chromate dip releasing hydrogen as a byproduct of the 
 attack. As the hydrogen is released from the metal surface, the pH of the solution near 
 the metal surface rises high enough to "deposit" a film of metal hydroxides and other 
 trapped ingredients from the solution. The film at first is a delicate gel, but quickly 
 hardens into a thin coating only a few millionths of an inch thick (or less). 
 
 The chromate film protects the plated metal from corrosion by acting as a barrier layer 
 against corrosive atmospheres. In general, the more hexavalent chromium trapped in the 
 film, the higher the coloration, and the better the corrosion resistance. 
 
 Since the chromate functions by attacking and dissolving some of the plated metal, 
 eventually the solution becomes so contaminated with plated metal, that it stops 
 producing acceptable coatings. At this point the chromate becomes "spent" and must be 
 waste treated. 
 
 Rinses following chromating operations are not recoverable (since recovery would only 
 hasten the demise of the chromating solution) and therefore must be routed to a 
 
 ® 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Pace 37 
 
wastewater treatment system before discharge to sewer. 
 
 Notes: 
 
 There are several variations on the chromating process, including some films that are 
 applied with reverse current and others that are applied and then "leached" to remove the 
 coloration. The most commonly applied chromates are the blue brights, followed by the 
 yellow and then the black. The military favor the olive drab for the color and high 
 corrosion resistance. 
 
 A significant amount of research is being made into substitutes for chromates that do not' 
 contain hexavalent chromium and recycling methods, although not much is on the market 
 at this time. 
 
 Some operations utilize a "bright dip" after zinc or cadmium plating. This dip can be used 
 by itself or before chromating. It provides no additional corrosion protection, but 
 enhances the appearance of the deposit by brightening the surface, which has a slight 
 "haze" in the as-plated condition.A bright dip solution is simply a very dilute solution of 
 nitric acid (0.25-0.50% vol) and water. The bright dip removes a thin organic film from 
 the surface of freshly plated zinc or cadmium, rendering the deposit far brighter than 
 before. This is not a chromate, nor a true conversion coating. 
 
 End Chapter 3 
 
 © 1994 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 38 
 
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Table of Contents 
 
 IV. Recycle and Recovery in Metal Finishing 
 
 Topic Page Number 
 
 Reducing rinsewater usage 
 
 1 
 
 Factors affecting drag-out 
 
 2 
 
 The single rinse 
 
 3 
 
 Counterflow rinsing 
 
 4 
 
 How dirty can a rinse be? 
 
 5 
 
 Drag-out rinsing 
 
 6 
 
 Agitation of rinses 
 
 7 
 
 Controlling water flow 
 
 8 
 
 Rinsing barrels 
 
 9 
 
 Drag-in-drag-out rinsing 
 
 9 
 
 Air-water sprays 
 
 10 
 
 Spray rinsing 
 
 11 
 
 Multiple use rinsing 
 
 12 
 
 What constitutes dilution? 
 
 13 
 
 Recycle/Recovery methods 
 
 14 
 
 What is Re-use recycling? 
 
 15 
 
 Evaporative recovery 
 
 17 
 
 Atmospherics 
 
 18 
 
 Vacuum 
 
 19 
 
 Vapor recompression 
 
 21 
 
 Electrolytic recovery 
 
 23 
 
 Ion Exchange 
 
 25 
 
 Reverse Osmosis 
 
 31 
 
 Electrodialysis 
 
 33 
 
 Other Membrane systems 
 
 34 
 
 Others 
 
 35 
 
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Part IV, Recycle And Recovery in Metal Finishing 
 
 REDUCING RINSEWATER USAGE 
 
 The more rinsewater that is used by a metal finishing facility, the larger the 
 wastewater treatment system or recovery system will be, the more it will cost, the 
 more difficult it will be to obtain consistent compliance with regulations, and the 
 more chemicals and sludge, will be generated. There is therefore, a great amount of 
 incentive for a metal finisher to reduce the amount of water that is used. 
 
 Rinsing processed parts adequately, with a minimum amount of water being used, 
 is a combination of art, and science. An experienced metal finisher will assure that 
 parts are properly drained, that rinsewater flow is at the minimum, and that the 
 process solutions are operated in such a manner that recovery of chemicals 
 dragged out of the process is feasible and optimized. 
 
 On the other hand, improper rinsing can lead to increased pollution loading at the 
 wastewater treatment system, contaminated solutions that need treatment or 
 disposal, and extremely high water and sewer bills. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 1 
 
Factors Affecting Draa-out: 
 
 • Solution Viscosity 
 
 • Part Geometry 
 
 • Drain Time 
 
 • Surface Tension 
 
 FACTORS AFFECTING DRAG-OUT 
 
 The highest effort in pollution prevention practice should be employed at reducing 
 drag-out from metal finishing processes. The quantity of drag-out produced by a 
 process depends upon a number of parameters, some of which are listed here. 
 
 The higher the viscosity of the process solution, the more liquid adheres to parts 
 leaving the tank and therefore, the higher the drag-out rate. To visualize this, 
 imagine dipping the part in honey and withdrawing it from the vessel. A lot of 
 liquid will "stick" to the part. Now, if the part is dipped in hot butter instead, the 
 liquid will run off in tiny rivulets and droplets, leaving little liquid behind. That is the 
 concept of viscosity. In plating, the viscosity of the process solution is determined 
 by the concentration of the ingredients. By running process baths with lower 
 concentrations, we reduce viscosity and drag-out. The more complicated a part 
 geometry is, the higher the drag-out, because drilled and blind holes trap liquid and 
 carry it out of the process. 
 
 The drain time is related to the drag-out for the first 15-20 seconds. During this 
 interval, liquid is running from the parts and hopefully, back into the process tank. 
 By draining for at least 15 seconds, we optimize the drain time and reduce 
 drag-out. Reducing surface tension may or may not reduce drag-out. Experiments 
 have shown that in certain solutions, reducing surface tension (by adding wetting 
 agent) may actually increase drag-out. You need to experiment to find out if this 
 will work for you. 
 
 The concentration of ions that tend to form insolubles affects drag-out adversely 
 also. The higher the concentration of ions such as sulfates, silicates, phosphates, 
 and carbonates are in a solution, the higher the drag-out tends to be. 
 
 © 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 2 
 
RECYCLEXRECOVERY METHODS 
 FOR METAL FINISHERS 
 
 Flow Work 
 
 Air 
 
 Agitation 
 
 Platei 
 
 Plate 
 
 THE SINGLE RINSE 
 
 A rinse tank should only be big enough to contain the largest part that is anticipated 
 to be processed. Other features of a modern rinse tank include a skimmer to float off 
 oil, a recirculating pump, prop mixer, or air agitation sparging system, and an entry 
 pipe that creates a sweeping flow of water from the bottom to the top (not important if 
 agitation is high enough). 
 
 The flow of water needed to obtain a certain concentration of contaminant in the rinse 
 can be calculated from the following equation for an "ideal" single rinse; 
 
 D X Ct = F X Cr 
 
 Where: 
 
 D is the drag-out rate (gal/hr or liters/hr) 
 
 Ct is the contaminant concentration in the process tank (ppm) 
 
 F is the rinse flow rate (gal/hr or liters/hr) 
 
 Cr is the concentration of the contaminant in the rinse tank (ppm) 
 
 For example, if a single rinse is used after a nickel plating tank (Ct = 75,000 ppm of 
 nickel metal) and the drag-out rate is 0.5 gallons per hour, and we want a maximum 
 of 5 ppm nickel in our rinse tank, then we would need: 
 
 F = 0.5 X 75.000 = 7,500 gallons/hr of rinsewater flowing in the tank. 
 
 5 
 
 © 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 3 
 
RECYCLE/RECOVERY METHODS 
 FOR METAL FINISHERS 
 
 Counterflow Rinse With n Tanks 
 D = Drag-out 
 
 
 Ci 
 
 
 F = Flow Rate 
 
 
 Ct 
 
 
 F = D 
 
 Cr 
 
 n 
 
 
 
 
 COUNTERFLOW RINSING 
 
 To reduce the quantity of water required to obtain a low contamination level in the 
 rinse prior to the next process, a counterflow rinse system can be employed The 
 term counterflow originates from the fact that the rinsewater flows in a direction 
 counter to the work flow. An ideal counterflow rinse can be described by the 
 equation: 
 
 F = D (Ct/Cr)"" 
 
 Where n is the number of separate rinse tanks in the counterflow system. 
 
 COMPARISON 
 
 Single Rinse vs 2 Tank Tank Counterflow 
 D = 0.5 gph, Ct = 75,000 ppm, Cr = 5 ppm 
 
 Single Rinse 
 
 F = 0.5 X 75.000 = 7,500 gph 
 5 
 
 2 Tank Counterflow 
 
 F 
 
 = 0.5 
 
 75.000 
 
 = 61.25 gph 
 
 5 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 4 
 
Here is a comparison of the amount of water it would take with a single rinse, vs a 
 two tank counterflow rinse, to achieve a rinse concentration of 5 ppm, if the 
 dragout rate is 0.5 gal/hour and the concentration in the process tank is 75,000 
 ppm. 
 
 If a three tank counterflow was used, the flow rate required to achieve 5 ppm in 
 the last rinse would be only 12.33 gal/hour! 
 
 While counterflow rinses are wonderful for reducing water consumption, they do 
 have drawbacks. For example, it is difficult to use counterflow rinses after acidic 
 solutions that attack coatings, such as chromates, because the additional acid 
 attack that may occur in the rinse tank(s) can yield poor chromate films that don't 
 meet specifications. Also, the first tank in a counterflow rinse system can get so 
 concentrated, that it needs to be ventilated just as if it were a process tank. 
 
 On manually operated lines, it is often difficult to convince personnel to use each 
 compartment of a counterflow rinse, since that is extra work effort. Skipping 
 compartments can result in rinse tanks containing too high concentrations of 
 contaminants and may result in the loss of a process solution due to 
 contamination. 
 
 HOW DIRTY CAN THE RINSEWATER BE? 
 
 ppm 
 
 PiBceding 
 
 Follo^ng 
 
 7500 
 
 Aik CIn 
 
 Aik Tin Plate 
 
 750 
 
 Aik CIn 
 
 Add Plate 
 
 750 
 
 Add Pickle 
 
 Add Plate 
 
 375 
 
 Sulfuric 
 
 Chrome Plate 
 
 50 
 
 Add Pickle 
 
 Cyanide 
 
 25 
 
 Chrome Plate 
 
 Dry 
 
 Note: Above are just guidelines, NOT to be taken Verbatim 
 
 It is impossible to provide truly useful rinse concentration levels to use in the 
 equations provided earlier, because each plant must deal with different base metal 
 alloys, different part geometries, and different processing chemicals. The above 
 data is therefore to be used only as a guide. Each plant must make calculations 
 based upon their own information and drag-out rate variability. 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 5 
 
If the process tank has a recovery device such as an evaporator, the rinse tanks 
 must be kept significantly "cleaner" because impurities will be recycled to the 
 process and can eventually cause rejects. Analytical history on the process can be 
 helpful in determining the rate at which impurities build up, so that purity targets 
 for the rinses can be established. For similar reasons, all rinses prior to and after 
 recovery systems should utilize deionized water exclusively. If tapwater is used, all 
 ions typically in tapwater, such as calcium, magnesium, iron, sulfate, phosphate, 
 carbonate, silicate etc. will accumulate in the process solution. 
 
 RECYCLEXRECOVERY METHODS 
 FOR METAL FINISHERS 
 
 Concentrate 
 
 Return 
 
 —Water In 
 
 Plate 
 
 Drag-Out Drag-Out Rinse 
 Rinse 1 Rinse 2 y f 
 
 Work 
 
 Flow 
 
 To Waste 
 Treatment 
 
 DOUBLE DRAG-OUT RINSE 
 
 DRAG-OUT RINSES 
 
 The most commonly used method to reduce the dragout rate from a process tank is 
 to employ a dragout rinse tank. A typical dragout rinse tank consists of a tank 
 equipped with a pump that discharges to the process tank. The drag-out rinse is filled 
 with deionized water and as evaporation in the process tank allow s, the rinsewater in 
 the drag-out tank is returned to the process tank along with whatever chemistry it 
 collected. 
 
 The efficiency of the process can be increased by utilizing two rag-out tanks in series, 
 as shown in the slide. Operators can get into trouble when drag-out rinses are not 
 efficiently returned to the process tank. If you wait too long, the drag-out tank 
 becomes almost as concentrated as the process tank and the drag-out tank is 
 useless. There is an optimum amount of time that the operator can wait before 
 returning the drag-out solution back to the process tank. This optimum time must be 
 calculated, based on the worst case of drag-out and then the return schedule must be 
 adhered to. If evaporation losses from the process are too low, drag-out tanks 
 
 © 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 6 
 
become useless, unless auxiliary evaporation can be installed. Drag-out tanks after 
 strong acid tanks are also essentially useless, if the additional time the part is in 
 the relatively strong acid in the drag-out tank causes rejects. 
 
 RECYCLEXRECOVERY METHODS 
 FOR METAL FINISHERS 
 
 AGITATION 
 
 RINSE TANK AGITATION 
 
 Because the modern rinse tank runs at very low rates of flow, agitation of the 
 rinsewater becomes very important. Without agitation, soils accumulate in the corners 
 of the rinse tanks and rinsewater can become stratified into layers. Shown here are 
 several methods of rinse tank agitation. The most popular method is air sparging, 
 using low pressure air blowers. A typical air agitation rate is 2cfm of air per square 
 foot of rinse tank surface area (length times width). Air sparging is most popular 
 because it is the easiest method of agitation to install, is low in cost, and does not 
 consume valuable tank space (except for the sparger at the bottom). However, air 
 agitation normally does not do an effective job of eliminating dead zones in a tank. 
 You can normally see dirt in the corners of air agitated tanks. You can even get into 
 OSHA trouble by air agitating the concentrated first rinse of certain counterflow 
 rinses! 
 
 By physically moving the rinsewater through use of a recirculating pump or prop 
 mixer, all dead zones are eliminated and mixing is at peak efficiency. Prop mixers 
 pose safety hazards (unless a safety ring is welded to the prop) and take up space 
 within the rinse tank (pumps do too). They also consume more energy to operate. 
 Ultrasonics are sometimes added to rinses in aerospace applications, where the 
 sonication removes debris that may be trapped in crevices or blind holes. Ultrasonics 
 in rinses for improvement of mixing the rinsewater is difficult to justify by economics 
 alone. 
 
 © 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 7 
 
CONTROLLING WATER FLOW 
 
 • Turn Valves Back 
 
 • Restrictors 
 
 • Timers 
 
 • Conductivity Controllers 
 
 • Flow Meters 
 
 CONTROLLING WATER FLOW 
 
 Rinsewater should only be flowing when the rinse tank contains water that is too 
 dirty for the next process tank. Therefore, a significant amount of water can be 
 wasted if the rinse tank is allowed to flow continuously. While several methods of 
 controlling water flow are listed here, experience has shown that flow restrictors 
 and conductivity controls yield the most success. Conductivity controller probes 
 are very sensitive to contamination by floating oil/debris. Some manufacturers offer 
 probes that work on an "inductive loop" principle. These probes can be coated 
 with oil or grease and still read conductivity accurately. Fixed orifice flow 
 restrictors cost less money and are very effective in limiting water usage to the 
 prescribed amount, but they don't turn the water off when it is not needed. Over 
 time, the orifice will become larger than designed, so they need to be replaced and 
 monitored periodically. 
 
 If your work flow is sporadic and production rates are low (10 parts per day, for 
 example), counterflow rinses may be a waste of floor space and money. In such 
 cases, single rinses with conductivity controls should work equally well, at less 
 cost. 
 
 RECYCLEXRECOVERY METHODS 
 FOR METAL FINISHERS 
 
 HANDLING OF BARRELS 
 
 • Slow Withdrawal 
 (16-20 sec Drain) 
 
 
 • Use "Designated" 
 Barrels or Dangler 
 Sleeves 
 
 • Rotate ? YES/NO 
 
 • Large Tapered Holes 
 
 • Maintain Clips/Doors 
 
 © 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 8 
 
RINSING BARRELS 
 
 Rinsing barrels properly to reduce drag-out and rinsewater flow requirements is 
 extremely important, because the drag-out rates of barrels is very high (usually 1/4 
 gallon of drag-out per barrel). Barrels should be slowly withdrawn from the process 
 tank to allow for at least 20 seconds of hang time for proper draining. If the barrel 
 contains cup shaped parts, it should be rotated while it is held above the process 
 tank, otherwise rotating the barrel may actually increase drag-out. Some innovative 
 metal finishers utilize designated barrels for cleaning/pickling and then transfer to 
 other barrels designated for plating. The result is that the dangler stays metal free, 
 and does not contaminate the cleaners and acids with heavy metals. Angler 
 sleeves, when properly used do the same thing, without having to use designated 
 barrels. 
 
 The plating barrel should have the largest holes that will still hold the parts within 
 the barrel, to facilitate draining and improve plating efficiency. Holes tapered from 
 the outside in drain better than straight wall holes. Also, the doors and clips need 
 to be maintained to prevent parts from falling out and contaminating process and 
 rinse tanks. 
 
 RECYCLEXRECOVERY METHODS 
 FOR METAL FINISHERS 
 
 DRAG-IN-DRAG-OUT RINSES 
 
 Evaporation 
 
 Plate Rinse Rinse Rinse 
 
 -Work i» To Waste 
 
 Sequence: 1-6 Treatment 
 
 DRAG-IN-DRAG-OUT TANKS 
 
 A dragout tank is beneficial because it captures chemicals that are ordinarily 
 discharged to waste treatment and returns them directly to the process tank in the 
 most usable form. Platers often ignore an additional benefit that can be obtained 
 by entering the dragout tank with the work before going into the process tank. 
 This routinely returns drag-out solution to the process tank. This is extremely 
 useful for processes that operate at room temperature, such as cyanide zinc 
 plating. Theoretically, a well operated drag-in-drag-out system will reduce chemical 
 losses from the process by 50%. This system can also be used for acid dips and 
 cleaners. One disadvantage is the added labor on manually operated lines. Another 
 disadvantage is that the system can not readily be incorporated into existing 
 automated lines. 
 
 © 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 9 
 
AIR-WATER SPRAYS 
 
 A plant faced with a severe water shortage recently reduced water consumption in 
 their hand plating lines by 99%. They replaced all their running rinses with empty 
 tanks (no drains) and high pressure spray guns similar to paint spray guns. These 
 guns sprayed a lot of air and very little water. The line operators would hold the 
 processed parts inside the tank and spray rinse them for a few seconds. The 
 compressed air was quite useful for rinsing blind holes and crevices. With 
 designated rinse tanks and deionized water, there would be great possibility for 
 almost total recycle in manually operated process lines. 
 
 Disadvantages that must be considered include the need for high purity 
 compressed air, added labor, and the possibility of OSHA violations created by the 
 mist generated. 
 
 © 1994, Frank Altmayer, Scientific Control Labs. Inc, 
 
 Page 10 
 
RECYCLEXRECOVERY METHODS 
 FPR METAL FINISHERS 
 
 SPRAY RINSING 
 
 Properly designed and functioning spray rinses mounted at the top of a process 
 tank can reduce chemical losses from hot processes dramatically. We emphasize 
 hot because spray rinses add whatever water they spray to the process tank. 
 
 Spray rinses are essentially useless for processes that operate at temperatures 
 below 100 deg. F. 
 
 The design of the spray system is crucial to its success. The nozzles must be made 
 of materials that resist the chemicals in the tank. Furthermore, the spray nozzles 
 should be easy to clean, because they clog often. They should also utilize as little 
 water as possible to do the job. Spray nozzles are available for spraying most ny 
 pattern desired, ranging from conical to a flat fan. Chose the spray pattern that will 
 result in the most surface area being contacted by the spray for your part 
 geometry. This may require some experimentation. A rule of thumb says that if 
 60% of the part surface is contacted by the spray, spray rinsing will be effective. 
 For best efficiency, sprays should be operated on an automated basis, as parts 
 leave the process. Enough freeboard should be designed into the tank, so that 
 impingement of the spray onto the parts does not increase fugitive emissions from 
 the process and create a health hazard. 
 
 Clogging of spray nozzles will be minimized, if deionized or RO water is sprayed. 
 
 Air knives, also located just above the process tank, can reduce the volume of 
 dragout by forcing the solution dragged out back to the tank. The air used by air 
 knives must be clean and high in humidity, to prevent drying of residual process 
 solution onto the parts. 
 
 © 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 11 
 
RECYCLEXRECOVERY METHOEKS 
 FOR METAL FINISHERS 
 
 Multiple Use Rinsing 
 
 Water In 
 
 To Waste Tank Raised -A 
 Treatment 3” For Gravity 
 Flow 
 
 MULTIPLE USE RINSING 
 
 Why not use rinsewater that contains "compatible" contamination over again for 
 another process rinse? If this is possible, then water consumption would be 
 drastically reduced. In reality, this IS possible. For example, why not allow 
 rinsewater after an acid dip to actually flow by gravity to the rinse tank after 
 electrocleaning. Besides using half the amount of rinsewater, rinsing is actually 
 improved by the neutralization that will occur between the acid and the alkali from 
 the two rinses. A very large plant in the south was able to utilize this concept to 
 reduce water usage from 500 gpm to 54 gpm, without sacrificing any of their 
 quality. 
 
 This concept for rinsewater use reduction is extremely useful in cleaning, pickling, 
 and passivating lines. The major drawback is that the rinsewater that is re-used 
 must be compatible with the parts and the chemicals in the subsequent process. 
 For example, you can not run the rinsewater after chromating to the rinse ahead of 
 chromating because in-adherent chromate films would form on the parts, while 
 they are in the rinsewater. Another drawback is the fact that tanks must be 
 elevated about 2-3" for the water to flow by gravity. This can then result in tank 
 lines getting progressively taller down a process line, but this usually is not a big 
 problem. 
 
 © 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 12 
 
WHAT CONSTITUTES DILUTION? 
 
 1. No wastewater treatment in Metal Finishing Facility 
 
 2. Routing "Clean" Water to Sewer 
 
 3. Phony "Treatment" 
 
 WHAT DOES NOT CONSTITUTE DILUTION? 
 
 1. Flows that go to Treatment 
 
 2. Batches of concentrated wastes that are partially 
 treated and then routed to secondary treatment 3. 
 
 Dilution of a concentrated waste prior to treatment 
 
 WHAT CONSTITUTES DILUTION? 
 
 Dilution used for the purposes of obtaining an effluent that is in compliance with 
 Federally mandated discharge regulations, is against the law. Dilution is practiced 
 when: 
 
 1. A company performs little or no waste treatment, and runs enough water in 
 their rinse tanks or other processes to meet discharge concentration limits. 
 
 2. Rinse tanks are operated at flow rates far above those necessary to protect 
 subsequent processes. 
 
 3. A company routes non contact cooling water or other "clean" non-regulated 
 process water directly to sewer or to a process or rinse tank that drains to the 
 sewer without going through a pretreatment operation. 
 
 4. A company routes "clean" process water to a "sham" treatment system 
 operated in addition to the real pretreatment system. 
 
 WHAT DOES NOT CONSTITUTE DILUTION? 
 
 The following are not considered dilution: 
 
 1. Using a high rinsewater flow, if all flow is routed to waste treatment. In such 
 cases, the metal finisher is paying extra for wasted water and treatment chemicals, 
 and he might be affecting the performance of the pretreatment system, but he is 
 not diluting. 
 
 2. Treatment of a concentrated waste by batch, then routing the treated waste 
 through the pretreatment system at low flow in order to obtain secondary 
 treatment. 
 
 © 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 13 
 
3. Dilution of a concentrated spent process solution prior to treatment, as required 
 to ensure safety and proper treatment (some are dangerous to treat when 
 concentrated). 
 
 MATERIAL RE-USE AND RECOVERY 
 
 1 Save Money 
 
 2. C^enerate Less Waste 
 
 3. Use Less Ctiemlcal 
 
 4. Become A "Good” Guy 
 
 RECYCLE/RECOVERY METHODS 
 
 Once rinsewater flow rates have been reduced to a minimum, the metal finisher 
 can review his processes and determine what, if any, recycle/recovery methods will 
 reduce his pollution loading to the wastewater treatment system. Recycle/Recovery 
 systems can reduce the amount of solid waste (F-006 filter cake) generated, and 
 can often yield savings in chemical costs that in some cases can pay for the 
 equipment and installation in a short time. 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 14 
 
WHAT IS RECYCLE / RECOVERY? 
 
 1. Material is re-used to make product 
 
 2. Material is substitute for product 
 
 3. Material is returned to process with no prior 
 "Reclaim" operation 
 
 WHERE MAY YOU FIND IT BEING EMPLOYED? 
 
 1. Recycle concentrates to processes 
 
 2. Recovery of metals from rinses 
 
 3. Sale of metal bearing wastes 
 
 4. Regeneration of process baths 
 
 5. Recycle of treated wastewater 
 
 WHAT IS RE-USE/RECYCLING? 
 
 Direct re-use involves the re-use of a waste material without processing it either as 
 a feed stock in a production process or as a substitute for a commercial product. 
 Reclamation or recovery removes impurities and recovers raw material or by¬ 
 products. 
 
 Solid Wastes are recycled when they are: 
 
 •Used or re-used in an industrial process to make a product. 
 
 • Effective substitutes for commercial products 
 
 • Returned to the original process without being first re-claimed 
 
 Technologies used for re-claiming are dictated by the type of waste and nature of 
 contamination, and fall into two basic categories: 
 
 1. Physical Separation 
 
 This makes use of differences in physical properties such as: 
 
 • Density 
 
 • Particle Size 
 
 • Boiling/Freezing Point 
 
 • Solubility 
 
 2. Chemical Separation 
 
 This makes use of chemical reactions to effect removal of 
 selected constituents in a waste. Examples: 
 
 • Precipitation 
 
 • Oxidation/Reduction 
 
 • Ion Exchange 
 
 • Electrolytic Recovery 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 15 
 
WASTES PRODUCED IN METAL FINISHING OPERATIONS 
 
 Primary wastes are derived mostly from: 
 
 1. Dumping of process solutions and related materials (cleaners, 
 acids, activating solutions, chromates, and stripping solutions) 
 
 2. Rinse water used to reduce the concentration of 
 processing chemicals to a safe level for the next process step 
 
 Other wastes are from maintenance operations and accidents such as spills, 
 overflows, filter maintenance. 
 
 Areas of metal finishing Operations Where Reuse/Recovery Technologies are 
 possible include: 
 
 OPERATIONS WHERE YOU MAY FIND RECYCLE/RECOVERY: 
 
 • Recycling concentrates to process baths through rinse tanks. 
 
 • Nonrecycle recovery of metals or concentrates. 
 
 • Selling By-product sludges 
 
 • Regenerating Process Baths 
 
 • Recycling Treated Wastewater 
 
 Reuse/Recycling Technologies in the Metal Finishing Industries 
 
 Some of the more commonly used reuse/Recycling 
 Technologies in the metal finishing industry are: 
 
 • Evaporation 
 
 • Electrolytic Recovery 
 
 • Ion Exchange 
 
 • Reverse Osmosis 
 
 Less commonly used reuse/recycle methods in Metal 
 Finishing are: 
 
 • Carbon Adsorption 
 
 • Crystallization 
 
 • Electrodialysis 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 16 
 
RECYCLEXRECOVERY METHODS 
 FOR METAL FINISHERS 
 
 Typical Installation: 
 
 A typical recycle/recovery system for a metal finishing process tank involves either 
 a drag-out tank, a counterflow rinse, or a combination of both. The water used in 
 the rinses should be de-ionized to protect the process solution from buildup of 
 dissolved minerals from tap-water. Such buildup can slowly make a process 
 solution contaminated to such an extent that it can become a total loss. The 
 recovery "unit" operates off either the drag-out tank, or the first rinse in the 
 counterflow rinse tank. There are numerous variations, but this is most often the 
 case. The recovery system may recover a part or all the chemicals in the process 
 drag-out, depending upon the technology. The rinsewater and any non recovered 
 discharge from the recovery system continues to flow to the wastewater treatment 
 system. 
 
 RECYCLE/liECOVEliY METHODS FOR METAL FINISHED 
 
 Typical Evaporation Rate From Process Tanks 
 
 100 
 
 Rate 
 
 (gph) 
 
 Evaporation Rate 
 
 Per 100 Square tt. Of Tank Surface Area 
 
 Air Agitated Process 
 
 No Air Agitation 
 
 Degrees F 
 
 200 
 
 A. EVAPORATIVE RECOVERY 
 
 Evaporation of water from processes that operate at elevated temperature can be 
 very significant and increase dramatically, as the solution temperature goes beyond 
 140 deg. F, or if the solution is air agitated. The evaporation rate is also dependent 
 upon the relative humidity in the air. For example, at 140 degrees, and 50% 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 17 
 
relative humidity, an air agitated tank, with 100 square feet of surface area may 
 evaporate 10 gallons of water per hour, while a non air agitated tank evaporates 
 only 4 gal/hour. At 160 degrees, the same numbers are estimated at 20 and 10 
 gal/hour, respectively. This evaporative loss creates "room", in the process tank, to 
 return a portion of the drag-out loss. This can be accomplished in several ways, 
 including simply manually returning the drag-out liquid to the process tank. When 
 the drag-out rate is high, however, there will not be enough room in the process 
 tank to efficiently return the dilute drag-out solution. An evaporator can then be 
 used to either create the additional room in the process tank, or to concentrate the 
 rinsewater so less volume goes back to the process tank. 
 
 Evaporators are commonly employed on chromium, nickel and cyanide copper 
 plating operations, although they are not limited to just these. Evaporators fall into 
 two general categories; vacuum and atmospheric. Vacuum evaporators recover a 
 concentrated process solution and condensed water (distillate) that can be re-used 
 as rinsewater, while atmospheric evaporators recover only the process concentrate. 
 There is a significant cost difference between the two evaporation systems, with 
 atmospherics typically costing around 10% that of vacuum systems. A common 
 misconception is that atmospheric systems use "free" energy. However, if they use 
 "plant air" that has been heated, they indirectly consume a significant amount of 
 energy. In hot, dry climates, atmospherics can be operated using "free" thermal 
 energy, but still require electricity for the pumps and blower. 
 
 RECYCLE/RECOVERY METHODS FOR METAL FINISHERS 
 
 Typical Installation, Atmospheric Evaporator 
 
 RECYCLE/RECOVERY METHODS FOR METAL FINISHERS 
 
 ATMOSPHERIC EVAPORATORS 
 
 Exhaust To < 
 
 Exterior 
 
 
 
 P ant Air 
 
 Atmosphenc 
 
 Evaporator 
 
 Process Tank 
 
 ATMOSPHERIC EVAPORATORS 
 
 These devices operate by spraying the dilute waste stream over packing media, grid, or 
 plates, and then blowing plant air over the packing, to effect evaporation. Advantages 
 include low cost and simple maintenance. A major drawback is the inability to evaporate 
 on days when air humidity levels approach 80-90%. In areas of general high humidity, the 
 solution to be evaporated will need to be heated to some degree. Atmospheric 
 evaporators generally have low capacities, ranging from 10-40 gal/hour, although they ^ 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 18 
 
can be installed in "series" to attain whatever rate is necessary (as long as dry air is 
 available). On cyanide solutions, atmospherics can aggravate carbonate buildup in the 
 plating bath due to carbon dioxide adsorption from the entrained air. This will then 
 generate waste, from the carbonate removal process. It can be very difficult to use 
 atmospheric systems on process solutions containing wetting agents, because large 
 volumes of foam can be generated. 
 
 RECYCLE/RECOVERY METHODS TOR MrAl FINISHERS ^ 
 
 Heated Atmospheric Evaporator 
 
 At least one manufacturer has offered an atmospheric evaporation system that includes 
 heating elements to improve evaporative efficiency on high humidity days. 
 
 VACUUM EVAPORATORS 
 
 There are a number of different evaporator designs on the market, normally differing in 
 how the vacuum is achieved (eductor, vacuum pump), or how much energy is employed 
 (single effect, double effect), or how much vacuum is achieved. The higher the vacuum, 
 the lower the temperature at which water will boil. By boiling the water off at lower 
 temperatures (110-130 deg F), the vacuum evaporators protect some delicate ingredients 
 of processing solutions that might decompose at higher temperatures. Advantages of 
 these systems include recovery of both a concentrate and condensed water, and 
 operation in all weather conditions. Disadvantages include high energy and maintenance 
 costs, and foaming of some process solutions (one evaporator manufacturer has a design 
 that can handle foam). 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 19 
 
RECYCLE/RECOVERY METHODS FOli METAL FINISHED 
 
 Vocuum Evaporators (Single EM 
 
 Cooling 
 
 Water 
 
 
 Vacuum Pump 
 
 T 
 
 Condensate 
 
 Vapor 
 
 Chamber 
 
 
 Dilute Waste 
 In 
 
 SINGLE EFFECT EVAPORATOR 
 
 A single effect unit usually uses steam to heat the liquid to its boiling temperature. The 
 steam is passed through a steam coil or jacket, and the vapors produced by the boiling 
 liquid are drawn off and condensed. The concentrated liquid is then pumped from the 
 bottom of the vessel. The process requires about 1200 BTU/lb of water evaporated. 
 
 There are a variety of designs on the market, including evaporators made out of glass, 
 stainless steel, and carbon steel. 
 
 Vacuum system designs generally vary in the method(s) used to develop a vacuum, some 
 using vacuum pumps, while other utilize eduction systems. In general, the higher the 
 vacuum achieved, the lower the boiling temperature of the dilute waste stream, but the | 
 higher the energy, maintenance, and equipment costs. Cyanide solutions concentrated at 
 lower temperatures do not tend to form carbonates to the same degree as with 
 atmospherics. 
 
 Vacuum evaporative systems consume considerable energy, and the condensing system 
 requires cooling water (which becomes heated and can be used elsewhere in the plant). 
 
 RECYCLE/RECOVERY METHODS FOR METAL FINISHERS 
 
 Vacuum Evaporators (Double Effect) 
 
 
 
 i 
 
 p- 1 ■ 
 
 1st Effect 
 
 r 
 
 to 
 
 ■ < 
 
 P. 
 
 Tji^ 
 
 2nd 
 
 
 _ 
 
 Effect 
 
 A X 
 
 MULTIPLE EFFECT EVAPORATORS 
 
 A multiple effect unit consists of a series of single effect evaporators. Vapor from the 
 first evaporator is used as the heat source to boil liquid in the second evaporator. Boiling 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 20 
 
is accomplished by operating the second evaporator lower than the first. The process can 
 continue for several evaporators (effects). Depending on the number of effects, multiple 
 effect units can require as little as 200 BTU/lb of water evaporated. 
 
 RECYCLE\RECOVERY METHODS 
 
 Vapar HT*<rnni|>r<*ssi<iri UriilN: 
 
 VKNT .1 
 
 I 
 
 
 rfKAT 
 
 E^ClIANaFP 
 
 >■ 
 
 
 I 
 
 l ANK 
 
 JL 
 
 POMP 
 
 VAPOR RECOMPRESSION UNITS 
 
 The vapor recompression evaporators use steam to initially boil the liquid. The vapor 
 produced is compressed to a higher pressure and temperature. The compressed vapor is 
 the directed to the jacketed side of the evaporator instead of using more steam, and is 
 thus used as a heat source to vaporize more liquid. These units require as little as 40 
 BTU/lb of water evaporated. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. P3.0'0 21 
 
The following data on evaporative systems was generated in a research project (Project 
 71) conducted by AESF (prices are 1980). 
 
 ECONOMICS OF USING EVAPORATIVE RECOVERY TECHNIQUES 
 
 Solution 
 
 Est. Recovery 
 (Kq/Dav) 
 
 Method 
 
 Value ($/yr. 1987) 
 
 Chromium 
 
 Plating Rinse 
 
 13 
 
 Vacuum 
 
 15,100 
 
 Chromium 
 
 Plating Rinse 
 
 85 
 
 Vacuum 
 
 98,756 
 
 Zinc 
 
 Plating Rinse 
 
 100 
 
 Vacuum 
 
 45,210 
 
 Chromium 
 Plating Rinse 
 
 75 
 
 Vacuum 
 
 87,120 
 
 Chromic 
 
 Acid Etch 
 
 275 
 
 Vacuum 
 
 319,440 
 
 Chromic 
 
 Acid Etch Rinse 
 
 21 
 
 Vacuum 
 
 24,374 
 
 Chromic 
 
 Acid Etch Rinse 
 
 95 
 
 Vacuum 
 
 110,352 
 
 Nickel 
 
 Plating Solution 
 
 34 
 
 Atmospheric 
 
 86,020 
 
 Chromium 
 Plating Rinse 
 
 45 
 
 Atmospheric 
 
 52,272 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 22 
 
RECYCLE\RECOVERY METHODS 
 FOR METAL FINISHERS 
 
 Ellectrolytlc Recovery-HSA Cell 
 
 Work 
 
 Water In 
 
 Recovered Metal 
 Bearing Solution 
 Following Chemical 
 Stripping 
 
 20% To Waste 
 Treatment 
 
 ELECTROLYTIC RECOVERY 
 
 This is a technology that uses special electroplating equipment to lower the concentration 
 of dissolved metals in drag-out rinses and concentrated rinse tanks. Benefits include 
 reduction of sludge generation, some electrolytic destruction of cyanide, and reuse or sale 
 of scrap metal plated out. Disadvantages include incomplete recovery (some waste is 
 generated), tendency to spontaneous combustion of plated metal, and energy costs. 
 Electrolytic systems fall into two primary categories: 
 
 a. Equipment for primarily removing metal from the wastewater stream, in a form that has 
 little recycle potential. 
 
 b. Recovery of metals with recycle of some other ingredient potential 
 
 The major difference between these systems is the type of cathode use to plate the metal 
 out of the wastewater. A "conventional" system might be "home made", and simply use 
 corrugated steel or stainless steel electrodes. A high surface area cathode system that 
 improves the efficiency of metal remove is available from one supplier. Another 
 supplier offered an "HSA" (high surface area) reactor that plated out cadmium from a 
 drag-out rinse and simultaneously destroyed cyanide by electrolytic oxidation. The 
 manufacturer is no longer in business, but the systems are still available on the used 
 equipment market. 
 
 Typical applications of these systems include after-acid-copper plating, cyanide cadmium 
 plating, cyanide zinc plating, and cyanide copper plating. While attempts have been made 
 to utilize these systems on nickel plating processes, the lack of a suitable insoluble anode 
 has held back most progress. 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 23 
 
ECONOMICS OF USING ELECTROLYTIC RECOVERY 
 
 Solution 
 
 Estimated 
 
 Recovery 
 
 Rate 
 
 Recovery 
 
 Technique 
 
 Reuse 
 
 Application 
 
 Metal 
 
 Value 
 
 ($/kg) 
 
 Recovered 
 
 Metal 
 
 Value 
 
 ($/yr) 
 
 Acid Zone 
 Concentrate from 
 Ion-Exchange 
 (2.5 g/L Zn) 
 
 5 kg/week 
 
 ISA 
 
 As Anodes 
 
 1.37 
 
 343 
 
 Nickel Plating, Drag- 
 out 
 
 23 kg/week 
 
 LSA 
 
 As Anodes 
 
 10.12 
 
 11.638 
 
 Copper Plating, 
 Off-line Drag-out 
 
 0.35 kg/week 
 
 LSA 
 
 Sold 
 
 1.81 
 
 32 
 
 Cadmium Plating, 
 Drag-out 
 
 0.7 kg/week 
 
 LSA 
 
 Sold 
 
 3.52 
 
 123 
 
 Acid Copper Plating, 
 Drag-out 
 
 23 kg/week 
 
 HSA 
 
 Sold 
 
 1.81 
 
 2,082 
 
 Acid Zinc Plating, 
 Drag-out 
 
 16 kg/week 
 
 LSA 
 
 As Anodes 
 
 1.37 
 
 1,096 
 
 Bright Nickel 
 
 Plating, Drag-out 
 
 30 kg/week 
 
 LSA 
 
 As Anodes 
 
 10.12 
 
 15,180 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 24 
 
RECYCLE/RECOVERY METHODS FOR MEIAL FINISHERS 
 
 Reciprocating 
 ■low Ion Exchange 
 
 Resin Beds 
 
 ION EXCHANGE 
 
 Ion exchange has been in use in the metal finishing industry for decades. One "centralized 
 recovery" facility in Minnesota utilizes ion exchange cylinders to remove dissolved metals 
 and cyanide from rinsewaters. The cylinders are rotated, and returned to the central 
 facility, where they are treated to either recycle beneficial materials, or are waste treated. 
 A typical metal finishing ion exchange system has a fixed bed of resin with the ability to 
 exchange or remove cations or anions such as chromates from rinsewaters. Ion exchange 
 is almost totally unaffected by the flow rate at which it is used, however, highly 
 concentrated inflows should be avoided, except for systems specifically designed for such 
 inflows. 
 
 The resins used for metals recovery typically are co-polymers consisting of styrene and 
 divinyl benzene in cationic or anionic form. In general, divalent and trivalent ions are 
 easier than monovalent ions, to remove using ion exchange. 
 
 When the useful capacity of the ion exchange column is exhausted, it is regenerated 
 using dilute acid (sulfuric or hydrochloric) for cationic resins, and sodium hydroxide 
 solution for anionic resins. Some cationic exchange systems us dilute acid followed by a 
 solution of sodium hydroxide. The hardware of pre-packaged units consists of pressure 
 vessels ranging from 2-6 feet or more in diameter, handling flow rates up to 300 gpm. 
 Custom made units, with 12 foot diameter columns, have been built to handle flows as 
 high as 1150 gpm. The loading typically is 10 gpm per square foot of resin cross section. 
 The chief advantage of ion exchange, is that it is selective in what it removes. In a 
 recycling application, that means that you don't recycle all the impurities along with the 
 beneficial material (this is not 100% true). Some resins (weak acid cationic) require close 
 control of the pH of the feed stream, with lower pH reducing the capacity of the resin, 
 and higher pH tending to clog the resin with solids (metal hydroxides). The systems also 
 have the drawback of not having suitable instrumentation to tell when the resin is 
 saturated. Saturated resin will discharge an effluent containing high concentrations of the 
 pollutant it is supposed to remove. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. P3.g0 25 
 
ECONOMICS OF USING ION EXCHANGE FOR RECYCLE/RECOVERY 
 
 Solution 
 
 Estimated 
 
 Recovery 
 
 Rate 
 
 Recovery 
 
 Technique 
 
 Chromic Acid 
 Etch Rinse 
 
 45 kg 
 
 Cr/day 
 
 Ion Exchange 
 
 Evaporation 
 
 (Vacuum) 
 
 Hard Chrome 
 Plating Rinse 
 
 151 kg 
 Cr/wk 
 
 Ion Exchange 
 
 Evaporation 
 
 (atmospheric) 
 
 Sulfuric Acid 
 Pickle Solution 
 
 275 
 
 tons/year 
 
 Ion Exchange 
 
 Nickel Plating 
 Rinse 
 
 130 kg 
 NiS 04 /wk 
 
 Ion Exchange 
 
 Evaporation 
 
 (vacuum) 
 
 Chrome Plating 
 Rinse 
 
 45 kg 
 
 Cr/wk 
 
 Ion Exchange 
 
 Evaporation 
 
 (vacuum) 
 
 Acid Zinc 
 
 Plating Rinse 
 
 10 kg 
 
 Zn/wk 
 
 D.H. Ion 
 
 Exchange 
 
 Electrolytic 
 
 Chrome Plating 
 Rinse 
 
 85 kg 
 
 Cr/wk 
 
 Ion Exchange 
 
 Evaporation 
 
 (atmospheric) 
 
 Chrome Plating 
 
 18 kg 
 
 Ion Exchange 
 
 Rinse Cr/wk 
 
 Reuse Metal Recovered 
 
 Application Value Metal 
 
 ($/kg) Value 
 ($/yr) 
 
 Process 3.52 52,272 
 
 Solution 
 
 Process 3.52 26,576 
 
 Solution 
 
 Process 0.09 25.865 
 
 Solution 
 
 Process 1.76 11,440 
 
 Process 3.52 9,715 
 
 Solution 
 
 Sold 1.37 685 
 
 Process 3.52 14,960 
 
 Solution 
 
 Process 3.52 3,168 
 
 Solution 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 26 
 
RECYCLEXRECOVERY METHODS 
 FOR METAL FINISHERS 
 
 ION EXCHANGE FOR NICKEL 
 PLATING SOLUnONRECOVERY 
 
 Additional disadvantages include the requirement of additional treatment equipment for 
 modifying the regenerant stream to a chemistry suitable for re-use. An example is a nickel 
 recovery system, which requires de-acidification of the regenerant before it can be used 
 in the plating bath. The regenerant stream is not highly concentrated (2-4 oz/gal is 
 typical), and ancillary operations such as de-acidification require waste treatment of the 
 excess acid. The technique is considered to be an expensive recovery method that 
 requires a lot of care and knowledge of operation. 
 
 Ion exchange also can be used to remove specific ions from rinsewater at the rinse tank. 
 A typical application may be to remove nickel, copper (from an acid bath) or chromium 
 from their respective rinses and then to return the regenerated metal ions to the plating 
 bath as concentrates. 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc 
 
 Page 27 
 
Resin Types 
 
 Strong Acid Cation 
 
 2 (R-SO3H) + NiCl2 = (R-S03)2Ni + 2 HCI 
 
 Wide pH Range, H or Na Form, Large Vol. Regenerant 
 
 ( 1 ) 
 
 Weak Acid Cation 
 
 2(R-COOH) + NiCl2 = (R-COOH)2Ni + 2HCI 
 pH >6, H Form, Less Acid Required For Regen. 
 
 ( 2 ) 
 
 Strong Base Anion 
 
 R -NH3OH + HCI R-NH3CI + HOH 
 
 Wide pH Range, Neutralize Acid, Large Vol Regenerant 
 
 ( 3 ) 
 
 Weak Base Anion 
 
 R--NH2 + HCI R-NH3CI 
 
 pH <7, Low Alkalinity, Small Vol Regenerant 
 
 ( 4 ) 
 
 Heavy Metal Selective Chelating 
 
 2(R-EDTA-Na) + NiCl 2 = (R-EDTA) 2 Ni + 2NaCI (5) 
 Similar to Weak Acid Cation But Highly Selective 
 
 Resin 
 
 Types 
 
 Ion exchange resins are classified as cation exchangers, which have positively charged 
 mobile ions available for exchange, and anion exchangers, whose exchangeable ions are 
 negatively charged. Both anion and cation resins are produced from the same basic organic 
 polymers. They differ in the ionizable group attached to the hydrocarbon network. It is this 
 functional group that determines the chemical behavior of the resin. Resins can be broadly 
 classified as strong or weak acid cation exchangers or strong or weak base anion 
 exchangers. 
 
 Strong Acid Cation Resins. 
 
 Strong acid resins are so named because their chemical behavior is similar to that of a 
 strong acid. The resins are highly ionized in both the acid (R-SO3H) and salt (R--S03Na) 
 form. They can convert a metal salt to the corresponding acid by the reaction shown in the 
 slide. 
 
 The hydrogen and sodium forms of strong acid resins are highly dissociated and the 
 exchangeable Na+ and H+ are readily available for exchange over the entire pH range. 
 Consequently, the exchange capacity of strong acid resins is independent of solution pH. 
 These resins would be used in the hydrogen form for complete deionization; they are used 
 in the sodium form for water softening (calcium and magnesium removal). After exhaus¬ 
 tion, the resin is converted back to the hydrogen form (regenerated) by contact with a 
 strong acid solution, or the resin can be converted to the sodium form with a sodium ^ 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. Pa .50 28 
 
chloride solution. For Equation 5, hydrochloric acid (HCI) regeneration would result in a 
 concentrated nickel chloride (NiCI2) solution. 
 
 Weak Acid Cation Resins. 
 
 In a weak acid resin, the ionizable group is a carboxylic acid (COOH) as opposed to the 
 sulfonic acid group {S03H) used in strong acid resins. These resins behave similarly to 
 weak organic acids that are weakly dissociated. 
 
 Weak acid resins exhibit a much higher affinity for hydrogen ions than do strong acid 
 resins. This characteristic allows for regeneration to the hydrogen form with significantly 
 less acid than is required for strong acid resins. Almost complete regeneration can be 
 accomplished with stoichiometric amounts of acid. The degree of dissociation of a weak 
 acid resin is strongly influenced by the solution pH. Consequently, resin capacity depends 
 in part on solution pH. A typical weak acid resin has limited capacity below a pH of 6.0, 
 making it unsuitable for deionizing acidic metal finishing wastewater. 
 
 Strong Base Anion Resins. 
 
 Like strong acid resins, strong base resins are highly ionized and can be used over the 
 entire pH range. These resins are used in the hydroxide (OH) form for water deionization. 
 They will react with anions in solution and can convert an acid solution to pure water 
 Regeneration with concentrated sodium hydroxide (NaOH) converts the exhausted resin to 
 the hydroxide form. 
 
 Weak Base Anion Resins. Weak base resins are like weak acid resins, in that the degree of 
 ionization is strongly influenced by pH. Consequently, weak base resins exhibit minimum 
 exchange capacity above a pH of 7.0 These resins merely absorb strong acids; they 
 cannot split salts. The weak base resin does not have a hydroxide ion form as does the 
 strong base resin. Consequently, regeneration needs only to neutralize the absorbed acid. 
 Less expensive weakly basic reagents such as ammonia (NH3) or sodium carbonate can be 
 employed. 
 
 Heavy-Metal-Selective Chelating Resins 
 
 Chelating resins behave similarly to weak acid cation resins but exhibit a high degree of 
 selectivity for heavy metal cations. Chelating resins are analogous to chelating compounds 
 found in metal finishing wastewater; that is, they tend to form stable complexes with the 
 heavy metals. In fact, the functional group used in these resins is an EDTA compound. The 
 resin structure in the sodium form is expressed as R-EDTA-Na. 
 
 The high degree of selectivity for heavy metals permits separation of these ionic 
 compounds from solutions containing high background levels of calcium, magnesium, and 
 sodium ions. A chelating resin exhibits greater selectivity for heavy metals in its sodium 
 form than in its hydrogen form. Regeneration properties are similar to those of a weak acid 
 resin; the chelating resin can be converted to the hydrogen form with slightly greater than 
 stoichiometric doses of acid because of the fortunate tendency of the heavy metal complex 
 to become less stable under low pH conditions. Potential applications of the 
 chelating resin include polishing to lower the heavy metal concentration in the effluent 
 from a hydroxide treatment process, or directly removing toxic heavy metal cations from 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 29 
 
wastewaters containing a high concentration of nontoxic, multivalent cations. 
 
 Water Inlet 
 
 Ion €xchonQo 
 
 Water Outlet 
 
 : Backwash Controller 
 I Sight Glg^ 
 
 Upper Manifold 
 
 Nozzles 
 
 Resin 
 
 Regenerant 
 
 Meter 
 
 Graded Quartz 
 
 ower Manifold 
 
 Backwash Outlet 
 
 Ion Exchange Process Equipment and Operation 
 
 Most industrial applications of ion exchange use fixed-bed column systems, the basic 
 component of which is the resin column. The column design must: 
 
 • Contain and support the ion exchange resin 
 
 • Uniformly distribute the service and regeneration flow through the resin bed 
 
 • Provide space to fluidize the resin during backwash 
 
 • Include the piping, valves, and instruments needed to regulate flow of feed, regenerant, 
 and backwash solutions 
 
 End-of-Pipe Systems 
 
 Ion exchange can be used in two different ways for end-of-pipe pollution control. The 
 process has been demonstrated as a means of polishing the effluent from conventional 
 hydroxide precipitation to lower the heavy metal concentration further, and it has been 
 used to process untreated wastewaters directly for removal of heavy metals and other 
 regulated pollutants (not recommended, except in special cases). 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 30 
 
RECYCLEXRECOVERY METHODS ^ \ | 
 
 FOR METAL FINISHERS ] I 
 
 Reverse Osmosis 
 
 r J 
 
 
 ir 
 
 
 Rims Rims 
 
 Rinse 
 
 
 
 Reverse 
 
 Osmosis 
 
 Permeate 
 
 
 
 Concentrate 
 
 ^ Blowdown 
 
 To Waste Treat 
 
 REVERSE OSMOSIS 
 
 Reverse osmosis 
 
 (commonly called "RO"), is used to separate water from inorganic salts, through the use of 
 a "membrane" that allows transfer of water and "rejects" the salts. The system utilizes 
 pressures of 400-800 psi, generated by pumps to force the water through the membrane 
 ("permeate"), leaving a concentrated residual liquid ("rejectate") behind. To prevent 
 fouling of the membrane, feed solutions must be pre-treated to remove materials such as 
 manganese, calcium, lead, iron, carbonates, particulates, oils, and other fouling materials. 
 
 RECYCLEXRECOVERY METHODS 
 FOR METAL FINISHERS 
 
 HOLLOW FIBER MEMBRANE 
 
 HOLLOW FIBER MEMBRANE 
 
 PERMEATE 
 (RETURN TO 
 RINSE) 
 
 The membranes are made out of cellulose acetate (similar to the clear plastic covering 
 cigarette packages), aromatic polyamides, and cross linked polyamides. They come in 
 various configurations, including "spiral wound", "tubular", and "hollow fiber". The tubular 
 membrane is inserted onto or into the surface of a porous tube. This type of RO is used for 
 low volume (low pressure) applications. The spiral wound membrane is a flat sheet 
 separated by a mesh spacer that is spirally wound around a perforated plastic tube that 
 acts to channel the permeate flow. The hollow fiber membrane consists of millions of 
 membrane fibers. 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 31 
 
REXrYCLE/RECOVERY METHODS ] [ j 
 
 FOR METAL FINISHERS ^ J 1 ^ 1 
 
 RO IN NICKEL PLATING OPERATION^ 
 
 The most common (99%) of all recycling applications of RO is on the rinsewater of a nickel 
 plating tank. The rejectate is often too dilute to directly return to the tank, so evaporation 
 is often added to the system. RO systems have been developed to be used on alkaline 
 solutions such as cyanide copper and brass, but the rinse water must be filtered extremely 
 well, and must have a low carbonate level, and the water used in the plating and rinse 
 tanks must be deionized. Aside from the fouling problems, some RO systems are very 
 temperature sensitive. For example, a cellulose acetate membrane can not withstand a HP 
 temperature greater than 96 deg. F. The membrane also rapidly deteriorates if the pH of 
 the feed stream is less than 3 or higher than 10. Commercial systems that use RO 
 membranes outside this pH range do exist. In such applications, the membrane is designed 
 to be expendable and is more easily and economically replaced. 
 
 RO systems are also in use as a polishing operation after wasetwater treatment. The RO 
 system reduced total dissolved solids in the treated waste water, so that the water can be 
 recycled to the process. 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc 
 
 Page 32 
 
RECYCLE/RECOVERY METHODS 
 FOR METAL FINISHERS 
 
 Electrodialysis 
 
 Cathode 
 
 PUBiriKD 
 
 STBBAM 
 
 ELECTRODIALYSIS 
 
 Electrodialysis (ED) is a process which used a "stack" of closely spaced ion exchange 
 membranes through which ionic materials are selectively transferred or rejected. Driving 
 the ions through the membranes, is an electrical potential applied by a rectifier to two 
 electrodes as shown in the slide. In a plating operation, ED is typically applied to a rinse 
 tank after plating and the ED system separates the dissolved ions from the rinsewater. 
 Because each pass through the system does not create a very concentrated product 
 stream, the system is usually connected to a recirculating drag-out rinse tank. Typical 
 applications are on 
 
 drag-out tanks after gold, silver, nickel and acid tin plating tanks. On nickel plating 
 systems, ED does not remove organics from the rinsewater, thereby eliminating organic 
 contaminant buildup that would be obtained with evaporative systems. Disadvantages are 
 the same as those for RO, plus the cost of the equipment (very high). 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc 
 
 Page 33 
 
RECYClE/RECOVEliY METHODS FOR METAL HNISHERS 
 
 Membrane System For Recovery of Chromium From Rinsewaler 
 
 
 Anode 
 
 Chamber 
 
 OTHER MEMBRANE/ELECTROLYTIC SYSTEMS 
 
 There numerous other membrane based recovery systems on the market. Here is a 
 chromic acid recovery system that uses proprietary membranes and DC current to 
 concentrate chromic acid from rinsewater. Rinsewater is pumped into the catholyte 
 section of the cell and DC current causes the chromate ions which are negatively charged, 
 to migrate through the membrane into the anolyte chamber, where the chromate is 
 concentrated to several grams per liter. The recovered solution is then used for 
 evaporative make-up. Heavy metal contaminants are held back by the membrane and are 
 concentrated in the catholyte section. Liquid from the catholyte section is periodically sent 
 to waste treatment for heavy metals removal. The anodes and cathodes are typically 
 made of lead. 
 
 iPrYaE/RECQVERY MEIHODS FOR MElAl FINISHERS 
 
 Membrane System Fot Recoveiy ot Ctiiomium From Rinsewater 
 
 
 Work Flow 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 34 
 
RECYCLEXRECOVERY METHODS 
 FOR METAL FINISHERS 
 
 CRYSTALLIZATION 
 
 REYCLE\RECOVERY METHODS 
 FOR METAL FINISHERS 
 
 CARBON ADSORPTION 
 
 OTHERS 
 
 There are a number of other recycle and recovery schemes available to metal finishers. 
 Some, such as crystallization or freeze drying are extremely useful in special applications, 
 but are too expensive for general use in job shops. Others are "black boxes" that work by 
 some mysterious new (and highly questionable) discovery. In all cases the potential user 
 should thoroughly investigate the technology and avoid being a "pioneer". 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 35 
 
REFERENCES: 
 
 Nickel Plating, F. X. Carlin, Metal Finishing Guidebook & Directory, 1970 page 329. 
 
 Proceedings, Sur/Fin '92- Atlanta, Mark Ingle, James Ault, "Corrosion Control Performance 
 Evaluation of Environmentally Acceptable Alternatives for Cadmium Plating". 
 
 U.S. Patent 4,892,627, January 1990, K. Takata, "Method of Nickel-Tungsten-Silicon 
 Carbide Composite Plating". 
 
 Guide To Clean Technology, Alternative Metal Finishes, Mr. Paul M. Randall, USEPA Risk 
 Reduction Engineering Lab. Cincinnati OH (Unpublished Review Copy) 
 
 ADDITIONAL PUBLICATIONS: 
 
 Hazardous Waste Minimization Manual for Small Quantity Generators, Center for 
 Hazardous Materials Research, 320 William Pitt Way, Pittsburgh, PA 15238, 1987. (Call 
 1-800-334-CHMR.) 
 
 Waste Minimization Opportunity Assessment Manual, United States Environmental 
 Protection Agency, EPA 625/7-88/003, July, 1988 (NTIS) 
 
 Waste Minimization Audit Report: Case Studies of Minimization of Cyanide Waste from 
 Electroplating Operations, EPA 600/S2-87/056, January 1988 (NTIS). 
 
 Control and Treatment Technology for the Metal Finishing Industry - In-plant Changes, 
 EPA 625/8-82-008, January 1982. (Write to CERI,Technology Transfer, U.S. EPA, P.O. 
 Box 12505, Cincinnati, OH 45212) 
 
 ADDITIONAL POLLUTION PREVENTION INFORMATION CAN BE OBTAINED FROM: 
 
 Center For Hazardous 
 Materials Research (CHMR) 
 
 320 William Pitt Way 
 Philadelphia, PA 1 5238 
 (800) 334-CHMR 
 
 National Assoc. Of Metal Finishers 
 111 E. Walker Drive 
 Chicago, Illinois 60601 
 (312) 644-6610 
 
 Pollution Prevention Program 
 U.S. EPA Region III 
 841 Chestnut Building 
 Philadelphia, PA 19107 
 (215) 592-9800 
 
 © 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 36 
 
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Table of Contents 
 
 V. Pollution Prevention in Metal Finishing 
 
 Tooic 
 
 Paae Number 
 
 General Practice 
 
 1 
 
 Management Initiatives 
 
 2 
 
 Improved operating procedures 
 
 3 
 
 Technology modifications 
 
 4 
 
 Extending the life of solutions 
 
 5 
 
 Reducing drag-out 
 
 5 
 
 Recycling 
 
 7 
 
 Treatment alternatives 
 
 8 
 
 How basic metal finishing principles can affect waste generated 9 
 
 Drag-out volume 
 
 12 
 
 Temperature 
 
 12 
 
 How to start a pollution prevention program 
 
 13 
 
 Where does it come from? 
 
 16 
 
 Maintenance 
 
 17 
 
 Corrosion 
 
 20 
 
 Pilot studies 
 
 21 
 
 Inert anodes 
 
 21 
 
 Hand line operators 
 
 22 
 
 Filters 
 
 24 
 
 Spent solutions 
 
 25 
 
 Ventilation systems 
 
 25 
 
 Vapor degreasers 
 
 26 
 
 Chemical substitution 
 
 27 
 
 Trivalent for hexavalent chromium 
 
 29 
 
 Alkaline non-cyanide for cyanide copper 
 
 32 
 
 High pH nickel for cyanide copper strike 
 
 36 
 
 Acid salts for hydrochloric acid 
 
 37 
 
 Zinc-alloy for cadmium 
 
 39 
 
 Nickel-Tungsten-Silicon carbide for chromium 
 
 42 
 
 Carbon for electroless copper 
 
 45 
 

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Part V, POLLUTION PREVENTION IN METAL FINISHING 
 
 Setting up a good pollution prevention program need not be a difficult or expensive 
 undertaking. The essential preliminary step to any pollution prevention program is a waste 
 audit. The waste audit tracks your hazardous waste by monitoring all of the waste which 
 is produced at your facility to learn where it was generated. This results in a systematic 
 survey of a company's operations and is designed to identify areas of potential waste 
 reduction. The waste audit can be divided into six steps: 
 
 WASTE AUDIT STEPS: 
 
 . Identify hazardous substances in waste or emissions. 
 
 , Identify the sources of these substances. 
 
 Set priorities for various waste reduction actions to be taken. 
 
 . Analyze some technically and economically feasible approaches 
 to pollution prevention options. 
 
 Make an economic comparison of pollution prevention options. 
 
 . Evaluate the results. 
 
 Since pollution prevention is an ongoing effort, waste audits should be repeated at least 
 once a year. Document previous and current pollution prevention activities, evaluate their 
 effectiveness, and implement future actions accordingly. 
 
 GENERAL POLLUTION PREVENTION PRACTICE 
 
 Many pollution prevention practices are low-cost, low-risk alternatives to hazardous 
 waste disposal. Most of the approaches do not require a great deal of sophisticated 
 technology and can be relatively inexpensive. This and the following sections will 
 introduce you to general approaches to pollution prevention which should be considered 
 in any pollution prevention program. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 1 
 
Management Initiatives 
 Commitment/Involvement 
 1 St And Most Important Step 
 Foster Employee Awareness 
 Develop/Improve Facility Operating Procedures 
 
 Set Goals 
 Create Incentives 
 
 Management Initiatives 
 
 Management commitment and involvement is the key element in your pollution 
 prevention program. Being vital to the success of any pollution prevention program, 
 management initiatives should be considered as a preliminary step in your program. d 
 Effective management initiatives should foster employee awareness of, and participation 
 in, pollution prevention efforts and developing or improving facility operating procedures 
 to meet pollution prevention goals. Initiatives may include employee training sessions in 
 hazardous material handling and pollution prevention, 
 
 developing process documentation, and improving scheduling of processes. 
 
 Although pollution prevention commitments should begin with management, the 
 employees are often the best resource for suggesting improvements in the day-to-day 
 operations of the business. Employee incentive programs encourage employees to design 
 and use new pollution prevention ideas. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 2 
 
Improved Operating Procedures 
 
 Material and waste handling and storage improvements are the simplest and often most 
 effective first steps toward reducing wastes. Good operating practices involve the 
 procedural or organizational aspects of a manufacturing process and include the 
 following: 
 
 Improved Operating Procedures 
 
 Implement an effective inventory control system to enable you to 
 prevent waste generation due to unnecessary or excessive purchases 
 and through expiration of a product's shelf life. 
 
 Segregate waste streams to allow for certain wastes to be recycled 
 or reused and to keep non-hazardous materials from becoming 
 contaminated. 
 
 Improve material handling procedures such as using a minimum of 
 non-hazardous materials (e.g., absorbent, water) to clean up 
 hazardous material spills. 
 
 Prevent and contain spills and leaks by Installing drip trays and 
 splash guards around processing equipment. 
 
 Ensure that product and waste containers are kept closed except 
 when material is added or withdrawn. 
 
 Track wastes and include careful labeling to ensure safe handling 
 of wastes, and identification of wastes which have the 
 potential for recycling or resale. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 3 
 
Technology Modifications 
 
 Some products can be manufactured by two or more distinct processes, and one process 
 may produce less hazardous waste than the other. Technological modifications can be 
 generally categorized as: 
 
 Technology Modifications 
 
 Process modifications which may reduce raw material consumption, 
 increase production, and improve product quality as well as 
 reducing waste. 
 
 Equipment modifications, which can reduce or eliminate equipment- 
 related inefficiency. 
 
 Process automation, including use of automatic or mechanical 
 production devices or installation of computerized process 
 monitoring and adjustment systems, which may result in the 
 generation of less waste, the use of less energy and raw 
 materials, and the production of a higher quality or quantity of 
 product. 
 
 Changes in operation settings so optimum performance is achieved. 
 
 Water conservation which reduces the volume of wastewater 
 requiring treatment or disposal, and minimizes your water bill, 
 and 
 
 Energy conservation which minimizes wastes such as those 
 associated with water treatment, cooling water blowdown, and 
 boiler blowdown. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 4 
 
Extend The Life Of Process Solutions 
 
 . Replenishment of baths; by adding necessary chemicals bath life 
 may be increased. 
 
 . Use purer anodes, or regenerate plating solution through 
 filtration. 
 
 . Reduce drag-in by better or modified rinsing. 
 
 . Cover baths with lids when not in use. This will reduce product 
 losses through evaporation. 
 
 . Test process bath for pH, metals and other indicator parameters to 
 determine when additional chemicals should be added or when metal 
 contaminants should be removed. 
 
 . Properly design and maintain racks to reduce build-up of corrosion 
 and salt deposits which will contaminate plating solution. 
 
 Extend The life of Your Processing Solutions 
 
 The lifetime of a plating solution is limited by the accumulation of impurities and by 
 depletion of constituents due to drag-out. The build-up of impurities can be limited by the 
 following techniques: 
 
 Dragout Reduction 
 
 Plating solution which is wasted by being carried over into the rinse-water as a processed 
 part is moved from the processing solution into the rinse is defined as "drag-out", and is 
 the largest volume source of pollution. Numerous techniques have been developed to 
 control drag-out. The efficacy of any technique will function with the geometry of the 
 parts processed, operator technique used, racking methods, plating barrel design/loading, 
 transfer times, dwell times, and numerous other variables. 
 
 Reducing the dragout reduces the amount of rinse water needed. Also, less of the plating 
 solution metals leave the process, which ultimately produces savings in raw materials, 
 treatment and disposal costs. Dragout reduction techniques include the following: 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 5 
 
Reduce Solution Drag*Out 
 
 Lower the concentration of plating bath constituents. This will 
 save material cost, reduce solution viscosity and dragout, and 
 reduce the toxicity of bath solutions generated. 
 
 Increase plating solution temperature to reduce both viscosity and 
 surface tension of the solution. 
 
 Use nonionic wetting agents to reduce solution surface tension. 
 
 Withdraw work-pieces at a slower rate to allow maximum drainage 
 back into process tanks. 
 
 Install drainage boards between tanks to route dragout into the 
 correct process tank. 
 
 Properly design and maintain rack systems. Properly place 
 work-piece on the rack to reduce dragout. 
 
 Train personnel or program automatic machinery to allow for optimum drain 
 times 
 
 install drain bars on hand operated lines to allow workers to momentarily rest 
 the parts and drain them before moving to the next process. This normally 
 does not affect productivity significantly. 
 
 Install fog sprays or air knives on hot process tanks that can accept the added 
 liquid volume. 
 
 Rack parts for optimum drainage 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 6 
 
Reduce Water Usage 
 Install automatic flow controls. 
 
 Install multiple rinse tanks in a countercurrent series system. 
 
 Use sprays or mist to rinse off excess process solutions. 
 
 Agitate the rinsing-bath mechanically or with air to increase 
 rinsing efficiency. 
 
 Reduce Rinse Water 
 
 Rinse water reduction involves rinsing the work-piece in the most efficient manner, 
 thereby using the smallest volume of rinse water possible and in turn reducing treatment 
 needs, sludge generation, and ultimately saving money. 
 
 Recycling 
 
 Recycling is the use, reuse, or reclamation of a waste after it is generated by a particular 
 process. Examples of recycling opportunities include: 
 
 Recycling Process Solutions 
 
 Install rinse water treatment systems which recover process solutions 
 and allow recycling of the rinsewater. 
 
 Use spent acid/alkaline solutions to adjust the pH of the treatment 
 system. 
 
 Return spent plating solution to the manufacturer, whenever possible. 
 Recover plating metals from sludge. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 7 
 
Treatment Alternatives ^ 
 
 Finally, in some cases alternative treatment methods can reduce the toxicity or volume or 
 certain waste streams which cannot be eliminated. 
 
 For example: 
 
 Treatment Alternatives 
 
 Use treatment technologies which do not generate heavy metal 
 sludges such as ion exchange, evaporation, or electrolytic metal 
 recovery. 
 
 Use different precipitating agents which generate less sludge, 
 such as caustic soda instead of lime. 
 
 Reduction Of Waste Generation 
 
 We can reduce wastes generated by utilizing one or more of the 
 following: 
 
 Reduction Of Waste Generation 
 
 CHEMICAL SUBSTITUTION 
 WASTE SEGREGATION 
 PROCESS MODIFICATION 
 RECYCLE/REUSE 
 
 We shall define these and go into details shortly. But first, a word of caution: 
 
 Too often, advice is given or taken without complete understanding of the FULL 
 ramifications of a given waste minimization decision. At least one major captive plater 
 installed evaporative recovery with full intention of returning the concentrated brass 
 plating solution to the plating tank. Within one year after the installation was complete, 
 however, this same plater resorted to hauling the concentrate away rather than deal with 
 the rejects caused by the buildup of impurities. Is waste minimization practiced when the 
 waste is simply concentrated? The answer is NO. 
 
 There also is a significant amount of misinformation available as to what steps will result 
 in reduced waste. A case in point is a text on Waste Minimization that offers this advice: 
 "The plant currently treats chromium waste with sodium bisulfite to reduce chromium. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 8 
 
this requires the pH of the waste to be between 2 and 3. The acid used to lower the pH 
 and the caustic used to raise the pH will contribute to sludge volume. The company 
 should consider reduction with ferrous sulfide (typo. I think the author meant sulfate) 
 which doesn't require pH adjustment to 2." This is of course, totally erroneous and the 
 typo makes the information presented dangerous to boot! Ferrous sulfate generates four 
 times as much sludge as bisulfite in chromium reduction and clarification. 
 
 Another example of possibly bad advice: 
 
 " Plant A should consider replacing its cyanide process chemistries with chemistries that 
 do not contain cyanide.” Unfortunately, the processes referred to in plant A are Copper, 
 Cadmium, and Silver plating. Non cyanide copper plating is only in pilot plant stage, non 
 cyanide silver plating is available from only one supplier and is troublesome to operate, 
 and non cyanide cadmium plating can be non productive on heat treated parts. The point 
 to all this is that you can make intelligent decisions on waste minimization only after you 
 have obtained full knowledge about your process and the requirements placed on your 
 product. You must also have knowledge about how metal finishing principles can affect 
 waste generation. Nothing we present here will work in all cases and at all times. This 
 chapter intends to provide enough information (including potential problems) to guide you 
 in the direction of waste minimization. The final decision and responsibility will belong to 
 each individual facility. 
 
 How Basic Metal Finishing Principles Can Affect The Amount Of Waste 
 Generated 
 
 SOLUTION CHEMISTRY 
 
 A typical plating bath contains a compound that yields the metal ions for plating plus 
 other ingredients for: 
 
 Solution Chemistry 
 
 Conductivity 
 Anode Corrosion 
 pH Stabilization 
 Impurity Complexing 
 Brightening 
 Levelling Etc. 
 
 Solution chemistry can influence waste generation when the chemistry forms insolubles 
 during waste treatment. Ingredients that often form insolubles in waste treatment are: 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 9 
 
ingredients That Form Sludge 
 
 Sulfates 
 
 Phosphates 
 
 Silicates 
 
 Sulfides 
 
 Carbonates 
 
 Iron Compounds 
 
 By avoiding any of these ingredients in your processing chemistries or by reducing the 
 concentration of the compounds containing these ingredients, the quantity of waste 
 generated can be reduced. Of course, there are times when one or more of the above 
 chemicals is purposely added at the point of waste treatment to improve performance. 
 
 In such cases, be sure to add as little as is absolutely necessary and be sure the chemical 
 is truly needed. We recently visited a plant adding carbamates (organic sulfides) to 
 improve copper removal in their clarifier. When we tested their raw waste, we found their 
 dissolved copper was already far below regulated levels. The CLARIFIER was not doing 
 its job. Carbamates won't help In such cases. 
 
 REACTIONS AT THE CATHODE 
 
 At the cathode, we have two competing reactions: 
 
 Reaction At The Cathode 
 
 1. Metal Ions Are Converted To Solid Metal 
 
 2. Hydrogen Ions are Converted To Gas 
 
 Gas Evolution Reduces Solution Efficiency and Creates 
 
 Air Pollution 
 
 Reduce Hydrogen Evolvement By Maximizing Agitation, Temperature, Process 
 
 Chemistry 
 
 1. Metal ions are being reduced to solid metal by combining with electrons supplied by 
 the rectifier. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 10 
 
2. Hydrogen ions are similarly reduced by "competing" with the metal ions for the 
 available electrons. 
 
 As a result of these competing reactions, in most plating chemistries, some hydrogen is 
 evolved. This results in the discharge of hydrogen gas. The quantity of metal plated vs 
 the amount of gas discharged is known as the process "efficiency". Processes with low 
 efficiency generate a lot of gas and often require ventilation and scrubbing systems. 
 Scrubbing systems generate waste unless specifically designed to utilize recycling. The 
 efficiency of most plating processes can be maximized by use of good agitation (avoid air 
 agitation if possible), good pH control where applicable, frequent analytical control of the 
 chemistry, and operating at the upper end of the allowable temperature range. 
 
 REACTIONS AT THE ANODE 
 
 At the anode, we also have competing reactions: 
 
 Reactions At The Anode 
 
 1. Solid metal is converted to ions with help from the rectifier. 
 
 2. Hydroxide ions are converted to oxygen with help from the 
 
 rectifier. 
 
 Reaction 2, Creates Anode Sludge/Waste 
 
 Improve Anode Efficiency By: 
 
 Keeping hooks clean 
 
 Maintaining Correct Anode Surface Area 
 
 Good Agitation 
 
 Good Temperature Control 
 
 Use Correct Anode For The Process 
 
 If reaction 2 is allowed to proceed, the anodes become passive and the oxide film that 
 forms on their surface must be cleaned off...usually with strong acid pickles. Such 
 cleaning operations generate a significant amount of waste. Anode passivity can also 
 result in more solids being introduced into the plating solution (less filter life). Anode 
 efficiency can be improved by following the guide in the slide. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 11 
 
Drag>Out Volume Depends On: 
 
 Solution Viscosity 
 Part Geometry 
 Drain Time 
 Surface Tension 
 
 Metal Concentration In The Process 
 
 DRAG-OUT 
 
 Much waste minimization effort goes into reducing drag-out. The amount of waste 
 generated by dragout depends on a number of factors: 
 
 The last variable is a result of another metal finishing principle. When confronted with the 
 task of reducing waste generation, there is a temptation to reduce "Drag-Out" by 
 reducing the concentration of the process bath. This can be good or bad advice. 
 
 The plating principle at work here is an equation called the "Nernst Equation": 
 
 E = 
 
 E° 0.059 loo C 
 
 n 
 
 Where E is the theoretical plating voltage, E° is the standard electrode potential, and C is 
 the concentration of the metal ion. The more positive the value of E, the more readily the 
 metal deposits (plates). If we reduce the concentration of the metal ions (for example, if 
 we decided to plate with 22 oz/gal of chromic acid instead of 33), then E becomes more 
 negative and our efficiency drops dramatically. Small reductions in metal ion 
 concentration, however, can be successful if we keep in mind the impact on efficiency 
 and make appropriate adjustments such as decreasing current density, increasing 
 agitation and increasing the temperature. 
 
 Good agitation decreases the thickness of the cathode film where plating occurs. It also 
 increases the current density at which we can plate. The most popular method of 
 agitating is to use low pressure compressed air. While it Is the most popular, this method 
 of agitation is the least effective and produces waste due to the necessity of scrubbing 
 the exhausted air. You can also get into OSHA trouble by air agitating concentrated rinse 
 tanks (such as the first tank in a counterflow rinse) which do not normally have 
 ventilation hoods! 
 
 INCREASING TEMPERATURE 
 
 We've also mentioned increasing the temperature several times. What does this do for 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 12 
 
Increasing The Operating Temperature 
 Benefits: 
 
 Increases Ionic Activity 
 Increases Ion Diffusion Rates 
 
 The effect of increased ion activity and diffusion rates 
 is to counteract the negative effects of reduced ion 
 concentration. 
 
 Drawbacks: 
 
 Increased Brightener Consumption 
 Increased Cyanide Breakdown/Carbonate Buildup 
 Tank Lining Attack 
 Increased Energy Costs 
 
 By increasing process temperatures you will also get another side benefit....increased 
 evaporation. If you can increase the operating temperature you will have more room in 
 the process bath for you to return the plating solution from a dragout tank. 
 
 The drawbacks to increasing temperature include those shown on the slide. 
 
 How Should You Start Your Pollution Prevention Program? 
 
 A plant assessment is your first step. Analysis of operations can identify the plant 
 changes that will reduce chemical loss and water use. Resulting savings usually quickly 
 re-pay costs involved in implementing the program. 
 
 Typical steps involved in a plant assessment for pollution prevention purposes are: 
 
 1. Locate (or prepare, if necessary) plans or drawings of the layout of the metal finishing 
 area. These drawings should be to scale, identifying and showing the location of all 
 relevant equipment and tanks. Plating lines should be identified. Gutters, sumps and 
 sewer lines should be indicated. Water lines, control valves and flow regulators should be 
 identified. 
 
 2. With this information, you can now review and document all operations of the plating 
 room that relate to chemical or water use. Be sure to examine each plating line, as there 
 may be differences in sequence or plating requirements. The next slide shows examples 
 of the types of information you will be documenting. 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 13 
 
Starting Your PP Program: 
 
 1. Locate/prepare drawings/layout of facility 
 
 2. Review/document all operations where chemicals/water are used; 
 
 Estimates of production {i.e. square meters plated; number of 
 parts, barrels of racks to pass through a process line. 
 
 Purchases of chemicals and break-down of where each chemical is used, 
 how much... 
 
 Rinsing and draining times on automatic lines 
 
 Efficiency of operators in rinsing and draining on manual lines 
 
 Relative amount of dripping onto the floor, if applicable. 
 
 3. Now, you can examine process water use. Review past water bills to determine 
 expected water use, per day or minute. Measure and record water use at each process 
 step. Especially watch rinse flow rates, as this is where most water is used. (Water 
 meters on each line would be extremely useful). With these two sets of information, do a 
 water balance. A difference of 15 % or less is generally acceptable. If the variance is 
 larger, you should determine the reason. Here are some possible causes of such 
 differences: 
 
 wash-downs;- unattended running hoses; - non-rinsing uses of water, such as fume 
 scrubbers, heat exchangers, boilers, etc. 
 
 4. Your assessment will also include sampling and analysis to determine the nature and 
 characteristics of waste streams. Of course, the final effluent will be analyzed to 
 determine which pollutants are not in compliance with requirements. As part of the 
 assessment, you will also sample all individual rinse tanks, overflows, batch dumps, and 
 plating solutions (to allow calculations of drag-out). 
 
 These additional samples are used to isolate sources of pollution, to calculate chemical 
 losses, and to evaluate potential benefits of drag-out reduction and flow minimization 
 techniques. 
 
 5. You will also want to evaluate drag-out. Drag-out measurements are performed at 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 14 
 
starting Your PP Program 
 
 3. Examine Process Water Use 
 Water Bills 
 
 Measure Each Use 
 Balance (15% match desired) 
 
 4. Sampling and Analysis 
 Rinses 
 
 Spillage 
 
 Drippage 
 
 Drag-out 
 
 6. Quantify Drag-ou 
 
 6. Information On Spent Solutions 
 Cleaners 
 
 Acids 
 
 Chromates 
 
 Strippers 
 
 7. Analyze the Data 
 
 plating tanks to determine the pollutants contributed by these sources. This information 
 is used to evaluate the applicability and potential benefits of changes made to minimize 
 drag-out, and changes made to the rinsing systems. 
 
 6. You will collect information about batch dumps that result form the process. Batch 
 dumps can contribute significantly to effluent concentrations of pollutants, as well as 
 cause significant pH fluctuations in the plant wastewater stream. To obtain further 
 information about what happens in your operation, you might consider developing a 
 dump schedule and a simple materials balance for an individual department or processing 
 area. In a materials balance, you try to account for all materials that enter and leave a 
 processing area. This can help you improve process control, and improve other 
 operational aspects such as cleanup procedures. 
 
 7. Finally, use all this information to analyze the entire plating operation. Your 
 objectives are the elimination, recovery or reduction of wasted chemicals and wasted 
 water. Accomplishing these objectives will save you money, and at the same time reduce 
 or eliminate pollutant discharges from your plant. 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 1 5 
 
Where Does It Come From? 
 
 A. Maintenance 
 
 Implement An Inspection Program: 
 Flooring, Catwalks, Pits 
 Tanks, Tank Linings 
 Pumps, Pump Containment 
 Containment Dikes, Curbs 
 Ventilation System, Ductwork 
 Filters, Hoses, Heat Exchangers 
 Instrument Sensors 
 
 WHERE DOES IT COME FROM? 
 
 We can go a long way towards minimizing (and sometimes eliminating) waste, if we can 
 itemize the origin(s) of this adversary. So let's begin this section on Waste Minimization 
 by discussing the sources a metal finishing shop has available for the generation of 
 waste. Once this list of sources is refined for your individual plant, the next steps; was^ 
 reduction, substitution, recycling, and process modification may become "self evidenf’^P 
 Typical metal finishing processes and the wastes they generate are on the next page (A 
 more complete list of chemicals typically used in metal finishing is provided at the end of 
 this chapter). 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc 
 
 Page 16 
 
Typical Metal Finishing Processes and Wastes They Generate 
 
 Process 
 
 Heavv Metals 
 
 Cr^® 
 
 CN 
 
 FOG 
 
 SOLIDS 
 
 AIR EM 
 
 Acid Pickling 
 
 X 
 
 X 
 
 
 
 X 
 
 X 
 
 Alkaline Cleaning 
 
 X 
 
 
 X 
 
 X 
 
 X 
 
 
 Anodizing 
 
 X 
 
 X 
 
 
 X 
 
 X 
 
 X 
 
 Bright Dips 
 
 X 
 
 
 
 
 X 
 
 X 
 
 Chromating 
 
 X 
 
 X 
 
 
 
 X 
 
 X 
 
 Deburring 
 
 X 
 
 
 
 X 
 
 X 
 
 X 
 
 Degreasing 
 
 
 
 
 X 
 
 X 
 
 X 
 
 Electrocleaning 
 
 X 
 
 
 X 
 
 X 
 
 X 
 
 X 
 
 Electroless Plating 
 
 X 
 
 
 
 
 X 
 
 X 
 
 Passivating 
 
 X 
 
 X 
 
 
 
 X 
 
 X 
 
 Phosphating 
 
 X 
 
 X 
 
 
 X 
 
 X 
 
 X 
 
 Polishing/Buffing 
 
 X 
 
 
 
 X 
 
 X 
 
 X 
 
 Where Does It Come From? 
 
 Poor Maintenance 
 
 Inspect flooring 
 
 Inspect all tanks/linings 
 
 Inspect all pumps 
 
 Keep spare parts 
 
 Inspect containment systems 
 
 Inspect the ventilation system 
 
 Inspect all filter hoses and connections 
 
 Inspect heat exchangers, steam traps, and instrument sensors. 
 
 Maintenance 
 
 There are metal finishing plants where maintenance personnel seldom spend any time on 
 the plating equipment and infrastructure, and if they do, it is only because an emergency 
 has arisen. Maintenance personnel must be responsible for inspecting on a routine basis 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 17 
 
(weekly preferred) the infrastructure of the facility: 
 
 . Inspect flooring and repair any cracks subject to wetting by chemicals 
 immediately . Inspect joints and repair immediately if damage is detected. 
 
 . Inspect all tanks, tank linings for deterioration. Make immediate repairs on 
 repairs on tanks identified as "critical". If damage is detected, always inspect 
 the adjacent tank too. 
 
 . Inspect all pumps, focusing on seals and repair those identified as "critical" 
 immediately. Keep spare parts. 
 
 . Inspect containment dikes and other containment systems for signs of 
 leakage. Make repairs as soon as damage is found. 
 
 . Inspect the ventilation system for signs of damage to ducts, scrubbers, 
 packed towers, fans, fan belts, hoods. 
 
 . Inspect all filter hoses and connections. 
 
 . Inspect all heat exchangers, steam traps, and instrument sensors. 
 
 In some plants, it is still part of the routine, to hose down the outside of all tanks and the 
 superstructure with a high pressure water hose. This results in the generation of many 
 gallons of dilute waste that requires treatment and adds to the already accelerated 
 corrosion faced by all materials of construction in the facility. Maintenance personnel 
 should be trained to replace "hose downs" with "sponge-ups". At times, the sponged up 
 chemicals can be returned to the process tank. Even when this is not possible, smaller 
 volumes of concentrated clean up solution from segregated areas can be used for pH 
 adjustment. Another solution is to design the facility so that the exterior of the tanks 
 stay as clean as possible (drip pans, automated hoists, manual hoist systems), or to make 
 the tanks out of material that will allow the accumulated chemicals to remain without 
 trouble. You can also reduce waste from chemical spills by: 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 18 
 
Reduce Waste From Chemical Spills By: 
 
 Preventing the loss of chemicals to the environment as a result of 
 leaks, accidents and deliberate dumps. 
 
 Provide curbing around plating bath filters. 
 
 Route condensate from exchangers and coils in cyanide solutions 
 separately. 
 
 Use drain boards to prevent spillage between process tanks. 
 
 Prevent overflows from the "topping up" of process tanks. 
 
 Remove all valves from the bottoms of process tanks and rinse 
 tanks that contain concentrated rinsewater. 
 
 Inspect all tanks with bottom flanges and valves on a scheduled 
 basis. 
 
 Make chemical additions easy to do. 
 
 Prevent the loss of chemicals to the environment as a result of leaks, accidents and 
 deliberate dumps. Possible sources of accidental losses include tank leaks, equipment 
 leaks, spillage between process tanks, overflows, accidental opening or rupture of a 
 valve; and the spilling of chemicals in storage or during application. 
 
 Provide curbing around plating bath filters to recover leakage that is inevitable when 
 servicing/changing media. 
 
 Routing condensate from exchangers and coils in cyanide streams separate and directed 
 to the cyanide treatment system. Similarly, condensate from exchangers and coils in 
 chromium streams should be separately directed to the chrome treatment system. This 
 prevents the possibility of a toxic chromium-cyanide reaction. 
 
 Use drain boards to prevent spillage between process tanks. A drain board could be a 
 plastic coated drain tray, piping, or tank lining continued from one tank to the next. 
 
 Prevent overflows from the "topping up" of process tanks, by using spring loaded 
 nozzles, separate water lines, or float level controllers, if water is added directly from 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 1 9 
 
piping. 
 
 Remove all valves from the bottoms of process tanks and rinse tanks that contain 
 concentrated rinsewater. Seal the flanges at the bottom of tanks permanently. 
 
 Inspect all tanks with bottom flanges and valves on a scheduled basis (preferably 
 monthly). 
 
 Make chemical additions easy to do. Add only small amounts at any given time. Purchase 
 liquid concentrates instead of solids whenever economical (sometimes even when it 
 costs more). This is especially true with cleaners. However, acids should be replaced with 
 acid salts, if possible, due to the hazardous nature of liquid acids. Instruct operators to 
 dissolve all chemicals before they are added to process tanks. 
 
 Waste Generated by Corrosion: 
 
 Inspect metal tanks for stray currents and correct ASAP. 
 
 Avoid the temptation to line the inside and the outside of steel tanks because 
 it makes pinholes almost impossible to detect (until the tank coltapses). 
 
 Construct tanks of corrosion resistant materials such as polypropylene, 
 fiberglass, Kynar, stainless steel, and composites. 
 
 Protect all bare concrete surfaces subject to chemical spitls/sptashes with 
 sealing materials. 
 
 Corrosion 
 
 A significant amount of waste is generated either by combating or surrendering to 
 corrosion. Consider implementing an inspection program to protect against corrosion and 
 design corrosion resistance into your plant: 
 
 Pilot Studies 
 
 Avoid Accepting "free” Samples 
 
 Treat Waste From Pilot Studies 
 Separately or Return to Vendor 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 20 
 
Pilot Studies 
 
 That experimental line or testing bench tucked away in the bosom of your plating 
 department probably has accumulated many pounds of chemicals and chemical products 
 that were obtained "free" from suppliers or other shops (as they went out of business!). 
 Unfortunately, after such largess is accumulated, you usually find that much of it is 
 useless and must be disposed of. Your options are: 
 
 . "Lab-packs", cost of approximately $ 1000.00/drum. 
 
 . Bleed into your waste treatment system. 
 
 Neither option is highly desirable. The first is expensive while the second contributes to 
 a higher generation of hazardous waste. For example, each gallon of nickel plating 
 solution waste treated generates about 3.5 gallons of 2% solids sludge. Organic 
 chemicals are potential disasters. They are normally not compatible with waste 
 treatment systems and their presence is often cited for rejecting a waste from a disposal 
 facility. Be sure to check any organic containing product against the accompanying 
 MSDS for the presence of regulated/banned substances. When you find such chemicals, 
 attempt to locate a substitute that is not heavily regulated. If this is not possible, 
 purchase only the amounts you are sure to consume in a reasonable time frame. 
 
 Metal finishing laboratory discharges should be routed through the waste treatment 
 system, not directly to the sewer. 
 
 Inert Anodes 
 
 Because most plating baths work faster and with fewer contamination problems, when 
 the metal content is kept on the high side of the recommended operating range, plating 
 personnel naturally favor high metal concentrations. If you have a recovery system on a 
 plating process, it also will tend to increase the metal concentration of the plating 
 solution. This tends to be counterproductive, in that the higher the metal concentration, 
 the more metal is dragged out of the process tank and the more metal ends up in the 
 treatment system (resulting in more waste). 
 
 The answer is to use inert anodes wherever possible to compensate for the metal 
 returned by the recovery system. Try to operate the plating bath at the LOW end of the 
 acceptable concentration range. The benefits are: 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 21 
 
Using Inert Anodes 
 
 Less Drag-out....Less waste 
 Less waste from the scrubber 
 Smaller recovery system required 
 Less rinse water required 
 Lower fugitive emissions 
 
 On the negative side: 
 
 More frequent analysis 
 More sensitivity to contamination 
 Depending on the process, you may see a slower plating speed. 
 
 Hand Line Operators 
 
 Install Pulleys and Hoists To Reduce Floor Drips 
 Train Operators To Hold Parts 15-20 Seconds For Draining 
 Train Operators To remove Dropped Parts From Tanks ASAP 
 Train Operators To Properly Maintain Racks 
 
 Hand Line Operators 
 
 A lot of waste is generated when tank personnel remove racks of processed parts and 
 splash chemicals all over the floor. Often, this is not the fault of the personnel. Many 
 plating companies utilize racks that are oversized and unwieldy for one person to handle. 
 We have seen pulley systems installed over hand line tanks. These allow the operator to 
 easily hold the part over the tank for 15-20 seconds, allowing the process solution to 
 drain back to the tank. The rack can then be hand carried to the rinse tank. A manual or 
 automated hoist is, of course, the ultimate answer, but is often too expensive, or can nr+ 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 22 
 
be implemented in older shops with tank sequences that look like jig-saw puzzles. 
 
 Hand-line operators are also notorious for dropping parts into the process tanks and 
 leaving them there to form "sludge" which may not be removed until the annual shut¬ 
 down and clean-up of the tank. This also may not necessarily be the total fault of the 
 operators. Racks are often poorly maintained, contacts are heavily plated, preventing a 
 firm grip on the parts. There is no excuse, however, for not removing dropped parts from 
 tanks. 
 
 Hand Operated Barrel Lines 
 
 The above discussion for hand line operators, takes on a whole new meaning when 
 considered for hand operated barrel plating lines. 
 
 Here are approaches you should consider to reduce drag-out from barrel plating lines: 
 
 Reducing Waste From Barrel Lines 
 Slow Withdrawal 
 
 Rotate Barrel If Parts Are Complex/Cup Shaped 
 Tilt Barrel To One Side To Help Drainage 
 Use Barrels With Largest Holes 
 Maintain Barrel Holes/Doors 
 Use Designated Barrels, Whenever Possible 
 
 . Generally, slow withdrawal and draining over the plating tank reduces the 
 volume of drag-out by allowing more time for drainage back into the tank. 
 
 . The shape of the parts being plated will have an effect on barrel drag-out. 
 
 For simple parts which do not collect or hold solution, it is probably best that 
 the barrel not be rotated during withdrawal. On the other hand, if pieces will 
 tend to hold solution, barrels should be rotated during withdrawal and 
 drainage. (You could test a load with, and without rotation to decide the best 
 approach.) 
 
 . Use plating barrels with the largest holes possible. Newer designs with laser 
 drilled, tapered holes and with holes on the ends as well as the walls drain 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 23 
 
faster. Maintain the holes by drilling out accumulated fines that plug 
 small holes. Also maintain the doors, so small parts such as fasteners 
 don't fall out and end up as "sludge" at the bottom of the plating tank. 
 
 Consider using "designated" barrels for cleaning and acid dripping prior to 
 plating. The danglers won't get plated, resulting in lower metal contamination 
 of the cleaners and acid. This increases the life of the cleaners/acids, 
 reduces maintenance and "down time" of the barrels prior to plating, the 
 rinsewater after cleaning/acid dipping can often be discharged directly to 
 sewer (sometimes pH adjustment is needed). The disadvantage is the 
 added labor of unloading and re-loading the barrels midway through the 
 cycle. 
 
 Reducing Waste From Filters 
 
 Locate Inside Tank, Whenever Possible 
 
 Filters Outside Tank Should Be Contained 
 
 Connect To Tank Permanently, If Possible 
 (Avoid Hoses/Tubing) 
 
 Use Filters With Re-usable Media 
 
 Filters 
 
 Filters are a big potential source of waste. If your process filters are located outside the 
 process tank and are the type that require pre-coating or cartridge changes, you are 
 probably generating avoidable waste. Filters should be placed inside the process tanks if 
 possible. If they can not be placed inside the process tanks, they should be inside 
 containment trays, so that spillage that normally occurs during service, and leakage from 
 pumps/seals is collected for re-use or channeling to waste treatment. Some newer filter 
 designs incorporate elements that can be manually cleaned and re-used, eliminating the 
 need to dispose of spent cartridges, pads, and disks. Pumps should be located high 
 enough to prevent siphoning of process solution from the tank in event of malfunction. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 24 
 
Reducing Waste From Spent Solutions 
 Use Liquid Cleaner Concentrates Instead Of Powders 
 Use Weak Acids Or Acid Salts 
 Extend Chromate Life Through Chemical Control 
 Keep Acids At Low End Of Operating Temperature 
 
 Spent Solutions 
 
 Studies at various metal finishing facilities have shown that as much sludge is generated 
 from the cleaners, acids, and chromates and their associated rinses as is generated from 
 the plating rinses. Cleaners and acids become contaminated with heavy metals from the 
 danglers in plating barrels or from metal build-up on rack tips. Cleaners have a tendency 
 to accumulate solids at the bottom of the tank, from dropped parts and from additions of 
 powdered or granulated solid cleaner. One plater discovered his cleaners lasted three 
 times longer and were significantly more effective after he switched to a supplier of liquid 
 concentrate cleaners. The diluted concnetrate eliminated the need to dissolve solids, 
 saving labor as well. Acids should be kept as weak as possible to avoid unnecessary 
 attack of basis metal. Inhibitors are helpful as long as they do not contaminate the 
 plating solution. Chromate life can be extended by careful control of pH, keeping 
 immersion times as short as possible, and employing temperature control (keeping it at 
 the low end of the acceptable temperature range). 
 
 Waste From Ventilation Systems 
 Increase Freeboard On Ventilated Tanks 
 Use Correct Capture Velocity 
 Use Foam Blankets/Poly Balls 
 Recycle Scrubbing Water, If Possible 
 Use Updraft Ventilation, If Possible 
 
 Ventilation Systems 
 
 Your ventilation system can add to your waste generation in several ways. Scrubbers, 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 25 
 
I 
 
 de-misters, and condensate traps yield concentrated wastes that require treatment unlei^ 
 exhaust streams are segregated and collection/purification systems are employed. 
 
 Process solutions that generate mist (chromium plating baths, air agitated nickel/copper 
 baths etc.) should be in tanks with more freeboard. These processes should also employ 
 foam blankets, floating polypropylene balls, and updraft ventilation. Updraft ventilation. 
 Updraft ventilation allows mist to "condense" in the duct-work and flow back to the 
 process tank. Using the correct capture velocity is important. Too little ventilation air is a 
 safety and corrosion hazard, while too much creates excessive emissions and reduces 
 scrubber efficiency. 
 
 Reducing Waste From Vapor Degreasers 
 Keep High Freeboard 
 Use Refrigeration 
 Replace Old Degreasers 
 Add Cooling Coils 
 
 Train Operators At Slow Withdrawal 
 
 Locate Degreasers Away From Drafts 
 
 Vapor Degreasers 
 
 When toxic chemical release reports were first required, one plater was very surprised to 
 discover that he discharged over 60.000 lb of trichloroethylene (into the atmosphere) 
 annually! Frankly, this is very easy to do. The amount of solvent discharged into the 
 atmosphere can be affected by such diverse variables as freeboard, use of a lid, 
 ventilation rate, operating temperature, level of cooling/refrigeration, work withdrawal 
 rate, solvent density, and solvent stability. In one plant, the degreasers are located in the 
 vicinity of large overhead doors which the operators frequently leave open (to improve 
 the climate inside the shop). The uncontrolled drafts caused by the doors literally 
 vacuum the solvent out of the degreaser and work counter to the ventilation system. 
 
 The net result is significant loss of solvent and an unhealthy working environment. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 26 
 
CHEMICAL SUBSTITUTION 
 
 When pursuing a program of pollution prevention, the second alternative after elimination 
 is substitution. If we can substitute a process that generates less waste that the one 
 currently in use, we will be contributing to the prevention of pollution. Since there is no 
 "free lunch", we will be paying a price for this act and we need to know as much as 
 possible about the substitute process to make an intelligent decision so that the price will 
 not be too dear. The following are features of popularly touted substitutes for existing 
 coatings or chemical processes in metal finishing shops. 
 
 The incentive for substituting process chemicals containing non-polluting materials has 
 only been present in recent years with the advent of pollution control regulations. 
 Chemical manufacturers are gradually introducing such substitutes. By eliminating 
 polluting process materials such as hexavalent chromium and cyanide-bearing cleaners, 
 and deoxidizers, the treatments required to detoxify these wastes are also eliminated. It 
 is particularly desirable to eliminate processes employing hexavalent chromium and 
 cyanide, since special equipment is needed to detoxify both. 
 
 Substituting non-polluting cleaners for cyanide cleaners can avoid cyanide treatment 
 entirely. For a 2 gal/min rinsewater flow, this means a savings of about $12,000 in 
 equipment costs and $3.00/lb of cyanide treatment chemical costs In this case, 
 treatment chemical costs are about four times the cost of the sodium cyanide cleaner. 
 
 There can be disadvantages in using non-polluting chemicals. Before making a decision, 
 the following questions should be asked of the chemical supplier: 
 
 Substitution; Questions To Ask: 
 
 Are substitutes available and practical? 
 
 Will substitution solve one problem but 
 create another? 
 
 Will tighter chemical controls be required of 
 the bath? 
 
 Will the change involve any cost increases 
 or decreases? 
 
 Who Else Is Using This Process 
 Successfully? 
 
 How Long Has This Process Been On The 
 Market? 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 27 
 
Some commonly recommended chemical substitutes are: 
 
 Some Commonly Recommended Substitute Processes: 
 
 POLLUTING 
 
 Heavy Copper 
 
 Cyanide 
 
 Plating Bath 
 
 SUBSTITUTE 
 
 Copper Sulfate 
 
 COMMENTS 
 
 Excellent throwing power 
 with a bright, smooth, 
 rapid finish. A copper 
 cyanide strike may still 
 be necessary for steel, 
 zinc, or tin-lead base 
 metals. Requires good 
 pre-plate cleaning. 
 Non-cyanide process 
 eliminates carbonate 
 build-up in tanks. 
 
 Chromic Acid 
 
 Pickles, 
 
 Deoxidizers, & 
 
 Bright Dips 
 
 Sulfuric Acid 
 and Hydrogen 
 Peroxide 
 
 Chromium-free substitute. 
 Non Fuming. 
 
 Chrome Based 
 Anti-Tarnish 
 
 Benzotriazole 
 (0.1-1.0% 
 solution in 
 methanol) or 
 water-based 
 proprietaries 
 
 Chromium-free substitute. 
 Extremely reactive, 
 requires ventilation. 
 
 Cyanide 
 
 Cleaner 
 
 Tri-sodium-Phosphate 
 And Proprietary 
 Cleaners 
 
 Cyanide-free cleaner. 
 Good degreasing when 
 hot and in an ultrasonic 
 bath. Highly basic. May 
 cause wastewater 
 treatment problems. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 28 
 
Chemical suppliers can also identify any regulated pollutants in the facility's treatment 
 chemicals and offer available substitutes. The federally regulated pollutants are cyanide, 
 chromium, copper, nickel, zinc, lead, cadmium, and silver. Local and/or state authorities 
 may regulate other substances, such as tin, ammonia, and phosphate. 
 
 Other Substitutes for Popular Metal Finishing Processes: 
 
 Trivalent for Hexavalent Chromium 
 
 Regulations under the Clean Air Act, along with local constraints on chromium emissions 
 to the air and water, plus the "stigma" hexavalent chromium has obtained as a health 
 hazard are the driving forces behind the push for substitution of hexavalent chromium 
 plating processes with baths made from trivalent chemistries. While the trivalent process 
 has produced "hard" chromium deposits exceeding .0005" in the research laboratory, at 
 the present time, there is no commercially viable hard chromium plating process using the 
 trivalent chemistry. 
 
 PROCESS DIFFERENCES: 
 
 Cr"" 
 
 Cr"® 
 
 Filtration 
 
 No 
 
 Air Agitation 
 
 No 
 
 Carbon Treatment 
 
 No 
 
 Heat/Cool 
 
 Yes 
 
 No Vent 
 
 Vent 
 
 No Scrub 
 
 Scrub 
 
 Less Energy 
 
 More 
 
 Proprietary Anodes (Cl) 
 
 No 
 
 Membrane Cells (SO 4 ) 
 
 No 
 
 Lead Anodes (SOJ 
 
 Yes 
 
 Burn Proof 
 
 No 
 
 Current Interrupt OK 
 
 Not OK 
 
 Analysis Important 
 
 Not As Much 
 
 pH Important 
 
 No 
 
 3-5 cents/ft^ 
 
 2-3 cents/ft^ 
 
 Corrosive Solution 
 
 No 
 
 Process Differences 
 
 The trivalent chromium plating process has been available to the plating industry since 
 1973. The chloride based chemistry came first and was followed by the sulfate based 
 process. The process requires filtration, air agitation, carbon treatment, and heating. The 
 chloride based process requires cooling in addition to heating. The hexavalent process 
 functions very well without any of these, except for heating/cooling. The trivalent 
 processes operate within OSHA standards without direct ventilation, while the hexavalent 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 29 
 
bath must have an installed exhaust/scrubber system. The trivalent baths use less energy 
 overall because no make up air is heated to compensate for loss through ventilation. The 
 trivalent baths do not need air permits and OSHA headaches are reduced. ^ 
 
 The chloride based process utilizes proprietary graphite anodes that are designed to * 
 prevent the formation of hexavalent chromium. These anodes disintegrate over time and 
 must then be replaced. The sulfate process utilizes lead or lead alloy anodes that are 
 encased in a cell. The cell has a membrane walls that allow transfer of electricity and 
 certain ions, but reject trivalent chromium, thereby preventing the formation of 
 hexavalent chromium at the anode. 
 
 The cell contains approximately 10% sulfuric acid which periodically (every 3-6 months) 
 requires changing and waste treatment (there will be some heavy metals in the acid, 
 including lead). The cell membranes have a finite life and are expensive to replace. They 
 also require careful handling to avoid damage and leaks. 
 
 One of the more unique features of the trivalent baths is that they are almost "burn" 
 proof. That is no matter how high the current density is, the deposit will not turn 
 powdery/grey. The throwing power of the trivalent process is exceptional, yielding 
 coverage around recesses and drilled holes that is far better than with hexavalent baths. 
 
 Trivalent baths tolerate current interruptions, while hexavalent baths produce dull white 
 deposits if the current goes off during the plating cycle. Trivalent baths can not tolerate 
 heavy metal contamination to the same degree as hexavalent baths. While hexavalent 
 baths can produce a beautiful decorative deposit while containing many thousands of 
 parts per million of heavy metal contaminants, trivalent baths are detrimentally affected 
 by several hundred parts per million of heavy metal impurities. Trivalent baths require g 
 routine purification and carbon treatment, while hexavalent baths do not. ^ 
 
 Analytical control of trivalent baths is more critical because these baths contain very low 
 concentrations of chromium (as little as 0.7 oz/gal vs 33 oz/gal for hexavalent baths). In 
 addition to bath chemistry, the pH of the trivalent baths must be monitored and 
 controlled while pH is not of concern in hexavalent baths. 
 
 After factoring chemical, analytical, waste treatment, waste disposal, and energy costs, 
 trivalent baths are slightly more expensive than hexavalent. Reported costs for trivalent 
 baths range 3-5 cents per square foot while hexavalent costs range 2-3 cents per square 
 foot. 
 
 Hexavalent baths do not promote corrosion, if the plating solution is not adequately 
 rinsed from crevices, while the trivalent processes can seriously deteriorate steel surfaces 
 if allowed to remain (especially chloride). This can be compensated through he use of a 
 "post treatment" following plating. Some of these post treatments contain hexavalent 
 chromium, thereby negating some of the benefits of substituting trivalent for hexavalent. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 30 
 
DEPOSIT DIFFERENCES: 
 
 
 Cr"® 
 
 Darker 
 
 Pleasing Light Blue 
 
 Poorer Corr. Res. 
 
 Better 
 
 Good Wear Res. 
 
 Same 
 
 No Thick Deposits 
 
 Thick Deposits 
 
 Deposit Differences 
 
 The trivalent processes tend to produce a deposit that is generally considered to be 
 darker in appearance that the hexavalent processes and baths that are carefully controlled 
 to yield an appearance that is extremely close to hexavalent deposits are inconsistent. If 
 impurities are not kept at a very low level, color matching of parts plated months apart 
 can become a difficult proposition. Trivalent baths produce a deposit that is 
 micro-porous. This enhances the corrosion resistance of the plated coatings when applied 
 over nickel plating that is greater than 0.00025" in thickness. When the nickel thickness 
 is less than 0.00025", the trivalent chromium provides less corrosion resistance than a 
 "crack-free" deposit from hexavalent baths because there is inadequate nickel to delay 
 the on-set of base metal corrosion through the normal distribution of the corroding 
 current over a larger area. Trivalent deposits in excess of 0.0005" tend to be stressed 
 and have very low corrosion resistance due to excessive porosity. 
 
 The wear resistance (hardness) of a trivalent chromium deposit is similar to that of a 
 hexavalent deposit. Stripping trivalent deposits with hydrochloric acid is difficult and 
 slow. Reverse current stripping is usually employed. This "resistance" to hydrochloric will 
 also affect the ability to measure the thickness using chemical stripping methods such as 
 the hydrochloric spot test. 
 
 POLLUTION PREVENTION POTENTIAL: 
 
 Cr""^ 
 
 Cr"® 
 
 5-10% As Much Sludge 
 
 More 
 
 No Reduction 
 
 Reduction 
 
 Higher COD 
 
 No COD 
 
 Recovery Possible 
 
 Possible 
 
 Pollution Prevention 
 
 Trivalent chromium chemistries can be expected to generate between 5 and 10% as 
 much solid waste from waste treatment of rinsewater, due to lower chromium content in 
 the drag-out, when compared to hexavalent baths ( assuming no recovery of drag-out). 
 Trivalent baths require no reduction step, only pH adjustment. This translates to lower 
 capital costs for waste treatment, and no "hexavalent" violations due to malfunctions of 
 the reduction system. For companies that must comply with COD (chemical oxygen 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 31 
 
demand) regulations, trivalent baths will increase your COD loading because they contain 
 a significant amount of organic additives. No exhaust from the process means no air 
 permit, no scrubbing equipment, and no treatment/disposal of scrubbing media. Suitable^ 
 recovery methods are available for both hexavalent and trivalent chemistries. * 
 
 WORKER SAFETY/ECONOMICS: 
 
 
 Cr"® 
 
 Not Carcinogen 
 
 Carcinogen 
 
 0.5 mg/M^ 
 
 0.05 mg/M^ 
 
 No Fire Hazard 
 
 Fire Hazard 
 
 Not Skin Corrosive 
 
 Skin Corrosive 
 
 More Expensive 
 
 Less Expensive 
 
 Color Problem 
 
 Color No Problem 
 
 Worker Safety/Economic Issues 
 
 Hexavalent chromium is listed as a suspected carcinogen, trivalent, at this time, is not. 
 OSHA regulates hexavalent chromium at 0.05 mg/cubic meter while trivalent chromium is 
 regulated at 0.5 mg/cubic meter. 
 
 Hexavalent chromium plating solutions and chemicals are fire/explosion hazards while 
 trivalent baths are not associated with such hazards. 
 
 At the present time, a metal finisher outside the USA with a hexavalent chromium platii® 
 process can successfully compete with a plater using the trivalent process on the basis of 
 economics and esthetics. A significant number of chromium platers in California have 
 substituted trivalent chromium for hexavalent baths. One plater operates both baths, and 
 reports that the hexavalent process consistently outperforms the trivalent process in 
 appearance. Another plater performing trivalent chromium plating only, dares anyone to 
 tells the difference. 
 
 Alkaline Non Cyanide Copper for Cyanide Copper 
 
 Since 1990, alkaline non cyanide copper plating processes have been available as 
 substitutes for the cyanide process. The obvious benefit is the elimination of cyanide 
 from the wastewater stream. Not so obvious benefits include faster barrel plating speed, 
 no cyanide in the F-006 waste from waste treatment (making delisting of the F-006 a 
 more likely possibility), lower sludge volume generation due to lower metal 
 concentrations, simplified wastewater treatment, no trouble with carbonate buildup, 
 elimination or reduction from TRI (Toxic Release Inventory aka "Form R") reporting, and 
 lower OSHA safety concerns. 
 
 While it is unlikely to happen on a frequent basis, if the cyanide copper solution ever 
 requires disposal the cost is astronomical compared to the alkaline non cyanide process. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 32 
 
Balancing the benefits are disadvantages such as; 
 
 Niger operating costs 
 
 Inability to use the process on zinc surfaces 
 (die castings and zincatedaluminum/magnesium) 
 
 Greater sensitivity to impurities 
 A chemistry that is more difficult to control 
 
 At least one of the non cyanide processes utilizes a "purification" cell in addition to the 
 normal plating tank. 
 
 PROCESS DIFFERENCES: 
 
 ANCC 
 
 CC 
 
 No Cyanide 
 
 Cyanide 
 
 pH 8.8-9.8 
 
 pH 10.5-14+ 
 
 Zinc Die Castings??? 
 
 !!!! 
 
 Faster 
 
 Slower 
 
 Purification Cell 
 
 No Cell 
 
 Filtration 
 
 Optional 
 
 Impurity Sensitive 
 
 Not Sensitive 
 
 Control Problems 
 
 No Problem 
 
 Excellent Cleaning Req. 
 
 Not Req. 
 
 Constant Dummying 
 
 Not Req. 
 
 Special Anodes 
 
 Not Req. 
 
 Process Differences 
 
 The non cyanide process operates at a pH range of 8.8-9.8 while the full strength 
 cyanide process is at pH 13-14 (cyanide strike baths for zinc die castings operate at pH 
 10-10.5). Despite the lower pH of the non cyanide process vs the cyanide process, the 
 non-cyanide bath has trouble tolerating zinc contamination and has not been highly 
 successful at depositing copper over zinc surfaces. Further research is presently under 
 way to improve on this drawback (and also to develop a non cyanide brass). Both 
 cyanide and alkaline non-cyanide copper processes operate at temperatures ranging 
 140-160 deg. F. The throwing power of the non cyanide process is superior to the 
 cyanide process. This is especially evident in barrel plating. The non cyanide process 
 utilizes cupric copper ions while the cyanide contains monovalent copper. This translates 
 to faster plating at the same current density for the cyanide process. However, the non 
 cyanide process can operate at higher current densities to yield faster plating overall. 
 Changing over to the non cyanide process requires a lined tank and purification 
 compartment outside the plating tank (for at least one of the commercial processes). 
 Good filtration and carbon treatment are mandatory for the non cyanide process, not 
 mandatory for the cyanide process. The cyanide process is more tolerant of poor 
 cleaning practices, while the non cyanide process requires excellent cleaning prior to 
 plating. The non cyanide processes use air agitation and at least one of them uses a 
 purification cell with proprietary anodes that prevent accumulation of too much cuprous 
 copper, while the cyanide process has no such requirement. 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 33 
 
DEPOSIT DIFFERENCES; 
 
 ANCC 
 
 CC 
 
 Fine Grained 
 
 Fine Grained 
 
 Less Pure 
 
 Pure 
 
 Dense 
 
 ■ I' 
 
 Dense 
 
 Deposit Differences 
 
 Both types of copper plating baths yield a fine grained, dense deposit of equal 
 metallurgical property, with the possible exception of purity, since the non cyanide 
 process incorporates a trace of organic into the deposit from the additives. An ideal 
 application for the non-cyanide process is for thick deposits used as heat treating 
 (carburizing) stop-off on steel parts. The dense deposit is an excellent diffusion barrier for 
 carbon. 
 
 
 Pollution Prevention 
 
 The cyanide and alkaline non-cyanide process function at elevated temperature, making 
 recovery through drag-out control and other recovery systems viable. The non cyanide 
 process contains 1/2 to 1/4 as much copper as a full strength cyanide copper bath, 
 translating to lower sludge generation. Waste treatment is accomplished by pH 
 adjustment with lime, or magnesium hydroxide, eliminating the two stage chlorination 
 system from the waste treatment system and eliminating use of more dangerous 
 chemicals such as chlorine or sodium hypochlorite. A potential negative pollution 
 prevention effect would occur if the non cyanide bath frequently became contaminated 
 beyond control (as happened during pilot scale testing in one case). The bath would then 
 require treatment/disposal. Much of the copper could be recovered through electrolysis 
 prior to such disposal, however. 
 
 Cyanide based copper plating solutions are far more tolerant of impurities and can last 
 many years before requiring treatment/disposal. In fact, there are baths that are 30 years 
 old or older out there! 
 
 The non cyanide process does not create a cyanide bearing F-006 waste. If copper 
 
 POLLUTION PREVENTION: 
 
 ANCC 
 
 CC 
 
 Recovery Possible 
 
 Also 
 
 Less Copper 
 
 More 
 
 Easy Waste Trt. 
 
 Harder 
 
 ^ No CN-FOOe 
 
 CN-F006 
 
 Short Life 
 
 Long Life 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 34 
 
plating on steel is the only source of cyanide in the F-006 waste, substitution of the non 
 cyanide process may create a waste that qualifies for "delisting". ERA could help by 
 promulgating a rule exempting waste from the treatment of rinsewater from alkaline 
 non-cyanide plating as they did for non cyanide zinc plating (on ferrous substrates). 
 Elimination of cyanide is one less TRI report also (but copper/copper compounds would 
 still be reportable). 
 
 WORKER SAFETY/ECONOMICS: 
 
 ANCC 
 
 CC 
 
 No Cyanide 
 
 Cyanide 
 
 No Chlorine 
 
 Chlorine 
 
 No Ozone 
 
 Ozone 
 
 No Caustic 
 
 Caustic 
 
 More Expensive 
 
 Up to 1/3 Less 
 
 Worker Safety/Economics 
 
 The non-cyanide process offers an obvious advantage in worker safety by the elimination 
 of cyanide. Cyanide catastrophes caused by accidental acidification of cyanide bearing 
 solutions would be eliminated. Cyanide oxidants such as chlorine, hypochlorite and ozone 
 would also be eliminated or reduced in usage. The lower alkalinity of the non cyanide 
 process offers less concern about caustic burns. 
 
 Platers using the cyanide based process, with waste treatment systems currently in place 
 for adequate treatment, currently have a decided competitive advantage based on 
 economics. As the cost of waste treatment/disposal increases in the future and added 
 pressure to reduce the publics' exposure to chemical catastrophes is created, more 
 platers will chose the non cyanide process. The additional demand for the process may 
 eventually result in lower costs. Some of the economic advantage of cyanide copper 
 processes could be reduced if ERA granted F-006 waste from non-cyanide copper plating 
 a RCRA exemption. 
 
 PROCESS DIFFERENCES: 
 
 NIQKEL 
 
 COPPER 
 
 High Metal Content 
 
 Much Lower 
 
 Ammonium Ions 
 
 No 
 
 Cleaning Important 
 
 Not As Much 
 
 Hard To Control 
 
 Easier 
 
 Dummying* Req. 
 
 No 
 
 *Dummying=Low Current Density 
 
 Electrolysis 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 35 
 
High pH Nickel for Copper Strike 
 
 High pH nickel plating solutions have been available for a long time as a substitute for 
 copper strike on zincated surfaces and zinc die castings. Cyanide copper has fewer ^ 
 cleaning and analytical requirements and has therefore been favored to the point of t 
 elimination of the nickel process from consideration. The nickel process deserves a new 
 look in light of the modern era of environmental concern. 
 
 Process Differences 
 
 Typical formulation/operating conditions for the nickel process are: 
 
 Nickel Sulfate: 10-15 oz/gal 
 
 Ammonium Chloride: 2-5 oz/gal 
 
 Sodium Sulfate (Anh): 10-15 oz/gal 
 Boric Acid: 2-3 oz/gal 
 
 pH: 5.3-5.8 
 
 Temperature: 70-90 deg. F 
 
 Current Density: 12-36 ASF 
 
 To obtain optimum results, the plater must balance the ratio between the nickel sulfate 
 and the sodium sulfate. Complex shaped parts require higher sodium sulfate 
 concentrations are employed. For operation above pH 5.4 ammonium hydroxide and 
 sulfuric acid are used for pH control. At the lower pH range, sodium hydroxide and 
 hydrochloric acid are used. Zinc contamination should be continuously removed through 
 low current density dummying in a purification cell. Cleaning prior to plating would be 
 more critical than for cyanide plating and equal to the effort for alkaline non-cyanide. ^ 
 Since the bath chemistry is not proprietary and there are no "additives" to purchase, tfw 
 cost of operating this bath would be expected to be less than for operating the cyanide 
 copper plating process and much less than operating the alkaline non cyanide process. 
 The process has been used successfully to plate zincated aluminum and zinc die castings 
 in the past. _ 
 
 DEPOSIT DIFFERENCES: 
 
 NICKEL 
 
 COPPER 
 
 Brittle 
 
 Soft 
 
 Poor Fatigue Strength 
 
 Strong 
 
 Porous 
 
 Dense 
 
 Passivation Problems 
 
 No 
 
 Deposit Differences 
 
 The higher the sodium content of this nickel plating bath, the more brittle the deposit 
 becomes. The bath should therefore be used only as a "strike" before conventional 
 nickel plating. Parts that undergo fatigue cycles or extreme temperature changes may 
 experience early fatigue failures and less corrosion resistance. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 36 
 
POLLUTION PREVENTION: 
 
 NICKEL 
 
 COPPER 
 
 No Cyanide 
 
 Cyanide 
 
 Cancer 
 
 No 
 
 Ammonium 
 
 No 
 
 More Sludge 
 
 Less 
 
 No CN-F006 
 
 Cn-F006 
 
 Pollution Prevention 
 
 Substituting nickel plating for cyanide copper eliminates cyanide from the rinsewater, 
 thereby yielding many of the pollution prevention benefits outlined for alkaline non 
 cyanide copper. The ammonium ion may cause waste treatment problems unless its' 
 concentration is minimized through drag-out recovery techniques. This bath contains a 
 higher metal content than the cyanide copper process and twice the metal content as the 
 alkaline non-cyanide process. Sludge volume from wastewater treatment would be 
 affected accordingly. 
 
 WORKER SAFETY/ECONOMICS: 
 
 NICKEL 
 
 COPPER 
 
 Lower Toxicity 
 
 Higher 
 
 Carcinogen 
 
 No 
 
 Nickel Itch 
 
 No 
 
 No "Catastrophe" 
 
 Possible 
 
 Cheap 
 
 More Expensive 
 
 Worker Safety/Competition 
 
 Since the bath operates at low temperatures, no ventilation would be required to control 
 emissions to workers' air. Nickel plating salts are far less toxic than cyanide, but they 
 have been tagged as suspected carcinogens and are on many companies' list for use 
 reduction. Overall safety to workers would be improved and probability of a catastrophic 
 accident would be eliminated when compared to cyanide copper. Worker safety level 
 would not be as good as obtained with alkaline non cyanide copper. 
 
 Plants using the high pH nickel process would be expected to have a favorable economic 
 advantage over plants with the alkaline non cyanide process and would have a slight 
 edge on plants with the cyanide copper process, if analytical and waste treatment 
 controls are kept under control. 
 
 Acid Salts for Hydrochloric Acid 
 
 Acid salts have a potential for replacing hydrochloric acid as a pre-dip prior to most 
 plating processes. Acid salts (Sodium, hydrogen, sulfate aka sodium bisulfate) are a 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 37 
 
crystalline material that is easily handled and less dangerous to store (no liquid spills). 
 
 PROCESS DIFFERENCES: 
 
 ACID SALTS 
 
 HYDROCHLORIC ACID 
 
 Powder 
 
 Liquid 
 
 No Smoke " 
 
 Old Smokey 
 
 Weaker 
 
 Stronger 
 
 Little Attack On Subst. 
 
 Attack 
 
 Process Differences 
 
 Acid salts are relatively mild and can not readily dissolve significant amounts of rust. 
 They presently find their greatest use in applications where a minor amount of de-rusting 
 and alkali neutralization is needed. However, through augmentation by either elevating 
 the temperature or adding cathodic power or both, the same benefits can be obtained 
 from acid salts as would be from hydrochloric acid. Hydrochloric acid has the advantage 
 of rapidly dissolving rust/corroslon products and having a greater capacity for alkali 
 neutralization. The acid salts do not rapidly attack metals, while hydrochloric acid does. 
 
 POLLUTION PREVENTION: 
 
 ACID SALTS 
 
 HYDROCHLORIC ACID 
 
 No TRI 
 
 TRI 
 
 Less Sludge 
 
 More 
 
 No Scrubbing 
 
 Scrubbing 
 
 Less Corrosion 
 
 Corrosion 
 
 Shorter Life 
 
 Longer Life 
 
 Pollution Prevention 
 
 Acid salts are not reportable under present TRI requirements. Because the attack on the 
 base metal is less severe, less base metal enters the rinsewater stream, resulting in the 
 generation of less sludge volume. Note: if the base metal is ferrous, less iron in the 
 sludge may "concentrate" artificially other metals in the sludge, yielding a negative 
 benefit. Hydrochloric acid requires ventilation and in most cases scrubbing of exhaust 
 fumes, while acid salts do not (unless electrolyzed during use). Scrubbing of exhaust 
 fumes generates additional waste requiring treatment. Hydrochloric acid is very corrosive 
 to the surrounding hardware such as tanks, piping, and structural supports. Acid salts are 
 less corrosive. Acid salts must be changed more frequently, since they are weaker, so 
 storage capacity for spent acid must be increased in the waste treatment system. 
 
 # 
 
 Page 38 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
, . ■ 1 ■ . , 
 
 WORKER SAFETY/ECONOMICS 
 
 ACID SALTS HYDROCHLORIC ACID 
 
 Less Skin Attack 
 
 More 
 
 No Spill Problem 
 
 Spill Problem 
 
 No Splash Problem 
 
 Splash Problem 
 
 Easy Clean-up 
 
 Hard 
 
 Expense Same as HCL 
 
 
 Worker Safety/Economics 
 
 Acid salts are far safer to handle than hydrochloric acid. When added to water, acid salts 
 may yield a sharp odor, but do not create voluminous white clouds of acidic fumes. 
 Worker safety is significantly improved. Spills of acid salts can readily be cleaned 
 up, while hydrochloric acid spills can be major disasters. 
 
 Metal finishers who are presently equipped to use hydrochloric acid with proper 
 environmental controls may have a slight economic advantage over those who would 
 require an acid salt solution that needs heating and or electrification. Intangible or difficult 
 to calculate cost savings such as improved worker safety and no TRI reporting could tip 
 the balance in favor of acid salts having the competitive advantage. 
 
 Zinc Alloy Processes for Cadmium Plating 
 
 When cadmium electroplate is used mostly for enhanced corrosion resistance to salty 
 environments, zinc alloy processes are suitable candidates as substitutes. Even pure zinc 
 is a suitable substitute for heavy cadmium deposits (more than 1 mil). When cadmium is 
 specified for enhanced lubricity, solderability, low electrical contact 
 resistance, ease of disassembly after corrosion has occurred, or to obtain benefits from 
 the toxicity of cadmium (organisms such as fungus or mold won't grow on it), zinc alloy 
 deposits may fail to be suitable substitutes. 
 
 While non cyanide cadmium processes are presently commercially available, the most 
 desirable substitute for a cadmium plating process would do away with both cyanide and 
 cadmium, so we will focus on such substitutes only. 
 
 PROCESS DIFFERENCES: 
 
 ZINC/ALLOY 
 
 CADMIUM 
 
 No Cyanide 
 
 Cyanide 
 
 Hard To Control 
 
 Easier 
 
 Cleaning Critical 
 
 No 
 
 Low Metal 
 
 High 
 
 Variety of Baths 
 
 No 
 
 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 39 
 
Process Differences 
 
 There presently are numerous zinc alloy processes commercially available, including 
 zinc-cobalt, zinc-nickel, zinc-tin, and zinc-iron. The corrosion resistance obtained from ^ 
 these alloys stems from the addition of a more noble metal than zinc in the alloy thereb* 
 reducing the activity of the metallic coating while maintaining the cathodic nature of the 
 coating for a steel substrate. Since there are many different processes available, we will 
 present only an overview of the differences. Whenever a single metal process is replaced 
 with a multi-metallic process, analytical control of the plating solution becomes far more 
 critical. If the more noble metal content in the alloy exceeds a certain amount, 
 chromating problems result. A wide variety of variables must be controlled to obtain the 
 "right" alloy composition, often including pH, temperature, chemistry, and agitation level. 
 
 Zinc-nickel alloys can be plated from a chloride based process similar to chloride zinc 
 baths or from an alkaline process similar to alkaline non cyanide zinc. Brightening agents 
 and other additives make the alloy processes more expensive to purchase and operate 
 than cyanide cadmium baths. The alloying metal is usually added as a chemical 
 concentrate that is purchased from the supplier. This allows for the use of zinc anodes, 
 since alloy anodes are not readily available or usable. 
 
 Cadmium can be plated from alkaline-cyanide, acid-non cyanide, neutral sulfate, and acid 
 sulfate chemistries. The alkaline cyanide bath contains from 20 to 36 g/L of cadmium 
 metal and as much as 150 g/L sodium cyanide. The neutral sulfate bath contains 4-10 
 g/L cadmium metal, but also contains up to 100 g/L of ammonium sulfate, yielding 
 wastewater treatment problems. The acid sulfate contains up to 10 g/L of cadmium 
 metal, the balance of the bath is made of 35 g/L sulfuric acid and additives. Cadmium m 
 can also be plated from a fluoborate chemistry, but the ingredients are expensive and t* 
 bath has poor throwing power. 
 
 DEPOSIT DIFFERENCES 
 
 ZINC/ALLOY 
 
 CADMIUM 
 
 Fine Grained 
 
 Yes 
 
 Soft/Harder 
 
 Soft 
 
 Non Toxic 
 
 Toxic 
 
 Hard To Solder 
 
 
 (except tin-zinc) 
 
 Easy 
 
 Stress Corr. Cracking 
 
 No 
 
 Good Adhesion 
 
 Better 
 
 Deposit Differences 
 
 Zinc alloy deposits are fine grained, and generally harder than cadmium or pure zinc. 
 Yellow chromates of the zinc alloys may have a significantly different appearance from 
 pure zinc. For example zinc-nickel may look purple when chromated. The zinc-nickel and 
 zinc-cobalt deposits can be very bright while the zinc iron and zinc-tin are less so. 
 Solderability is marginal for all but the zinc-tin alloy. Zinc alloy deposits are much hard^^ 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 40 
 
than cadmium and offer far less lubricity in torque tension applications, with the 
 impossible exception of zinc-tin.Cadmium has a fine grained structure that offers 
 excellent torque-tension properties (lubricity). Cadmium metal is toxic, so organisms such 
 as mold and fungus will not grow on cadmium plated surfaces. Corrosion products of 
 cadmium tend to readily break apart, while zinc and zinc-alloy corrosion products tend to 
 hold fast. 
 
 A recent study, made the following conclusions after comparing a large number of 
 environmentally acceptable substitutes (cyanide zinc was therefore omitted) to cadmium 
 (from the cyanide chemistry) in real-life outdoor exposure; 
 
 a. Corrosion Resistance 
 
 Cadmium, Ion Vapor Deposited Aluminum/topcoat, Zinc (alkaline process). Zinc (chloride 
 process), Zinc-Nickel (7-9% nickel) proved to be most effective corrosion protectors of 
 steel in natural marine, industrial, and rural atmospheres. Contrary to popular thought, 
 cadmium and zinc appeared to perform equally well in all three environments, including 
 marine exposure. 
 
 b. Torque-Tension 
 
 Cadmium, A proprietary calcium carbonate/sulfonate emulsion, water based zinc coating, 
 IVD Aluminum/Topcoat, Tin-Zinc, Zinc (alkaline process). Zinc (chloride process), and 
 Zinc-Nickel exhibited the lowest disassembly breaking torques. 
 
 c. Environmentally Assisted Cracking (EAC) 
 
 Cadmium was found to be the least likely coating to promote EAC (aka stress corrosion 
 cracking). The others all enhanced the susceptibility of high strength steel towards EAC, 
 with zinc-nickel and tin-zinc yielding the best performance of the alternates. The two 
 environments used in the experiment were 3.5% salt and oil/air. 
 
 d. Adhesion 
 
 The only plated coating to match the adhesion of cadmium was tin-zinc. The next best 
 plated coating was zinc-nickel. 
 
 POLLUTION PREVENTION 
 
 ZINC/ALLOY 
 
 CADMIUM 
 
 No Cyanide 
 
 Cyanide 
 
 Easy Waste Treat 
 
 Hard 
 
 No TRI 
 
 TRI 
 
 Easy Limits 
 
 Hard ,(.07mg/L) 
 
 Pollution Prevention 
 
 The zinc alloy processes offer the potential of eliminating two environmental hazards; 
 cadmium and cyanide. Waste treatment is normally accomplished by simply adjusting pH, 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 41 
 
thereby eliminating the need for cyanide oxidation. Regulatory compliance would be 
 easier to achieve since zinc and the alloying metal would have higher allowable discharge 
 concentrations than those imposed on the cadmium process. The zinc-cobalt, zinc-tin, 
 and zinc-iron processes do not add any metals that are presently regulated on the Fede^^ 
 level. The alloy processes are suitable for use with presently available recovery 
 technologies, although recovery may pose increased chemical control problems. 
 Substitution of a zinc alloy process for cadmium could remove another set of compounds ■ 
 that would normally be reportable under TRI reporting requirements. 
 
 WORKER SAFETY/ECONOMICS: 
 
 ZINC/ALLOY 
 
 CADMIUM 
 
 No Carcinogen 
 
 
 (except zinc-nickel) 
 
 Carcinogen 
 
 Low Toxicity 
 
 High 
 
 Low Dermal Corrosion 
 
 High 
 
 Moderate Cost 
 
 Same 
 
 Worker Safety/Economics 
 
 By eliminating cadmium and cadmium compounds which are toxic and suspected as 
 carcinogenic and by substituting a non cyanide process for one that typically contains 
 high concentrations of cyanide, worker safety would be significantly improved. 
 
 The economics of zinc-alloy plating depends on the process type chosen and its 
 application. There may be a cost savings, if compliance problems are factored in. 
 Unalloyed zinc plating will almost always be less expensive than cadmium. 
 
 Nickel-Tungsten-Silicon Carbide for Hard Chromium 
 
 This coating consists of a nickel-tungsten alloy deposit with silicon carbide particles 
 dispersed throughout the coating. The chemistry was patented by Takata in 1990 and is 
 currently under consideration by several large manufacturing companies as a substitute 
 for hard chromium. 
 
 PROCESS DIFFERENCES 
 
 Ni-W-SiC 
 
 CHROMIUM 
 
 pH 6-8 
 
 pH approx 3 
 
 175T 
 
 140°F 
 
 Current Density = 
 
 Current Density = 
 
 24-35 Adm^ 
 
 10-25 Adm^ 
 
 Process Differences 
 
 The alloy/dispersion coating contains nickel sulfate (35 g/L), sodium tungstate (65 g/L), 
 and ammonium citrate (110 g/L). Fine silicon carbide particles (30 g/L) are suspended g 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 42 
 
within the plating bath by continuous agitation. The silicon carbide particles are 
 incorporated into the deposit as it forms. The bath operates at pH 6-8 and is adjusted 
 with ammonium hydroxide or citric acid. Bath temperature is 150-175 deg. F. Plating 
 current density is 100-300 ASF. The hexavalent chromium chemistry contains chromium 
 trioxide (250 g/L) and a trace amount of sulfuric acid (2.5 g/L) or sulfuric acid (1.2g/L) 
 and a fluoride containing compound, yielding a fluoride ion strength of about 1 g/L. It 
 typically operates at 120-140 degrees F and at 150-300 ASF. 
 
 The alloy process can deposit the same thickness in half the time compared to a 
 conventional hard chromium process due to current efficiencies of 24-35% vs 10-12% 
 for conventional baths (one commercial chromium process operates at 25% current 
 efficiency and would therefore match the alloy plating speed). The alloy process has 
 significantly better throwing power, although complicated shapes still require auxiliary 
 anodes. 
 
 There presently is no good technique for stripping the alloy process, or performing "spot 
 repairs" while the chromium process is easily stripped and some parts can be spot plated. 
 The alloy process is sensitive to metallic contamination, while the chromium process is 
 very tolerant. Because the alloy process utilizes citrates at relatively neutral pH, it is 
 subject to biological activity such as mold/bacteria growth. 
 
 The alloy process utilizes a tungsten compound that is very expensive and difficult to 
 obtain. Some companies investigating the process have resorted to producing their own 
 sodium tungstate from other tungsten compounds. 
 
 DEPOSIT DIFFERENCES: 
 
 Ni-W-SiC 
 
 CHROMIUM 
 
 Softer 
 
 Harder 
 
 Better Wear 
 
 Excellent Wear 
 
 Less Corr. Res. 
 
 Better 
 
 Less Hydrogen 
 
 More 
 
 Deposit Differences 
 
 The nickel tungsten alloy has a slightly lower hardness when compared o chromium. The 
 wear resistance of the alloy is enhanced by the silicon carbide matrix which far exceeds 
 the hardness of chromium. The alloy performs better in abrasive wear applications than 
 chromium when tested with a Taber abrasion apparatus. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 43 
 
POLLUTION PREVENTION: 
 
 Ni-W-SiC 
 
 CHROMIUM 
 
 No Cr 
 
 Cr 
 
 W, Ni 
 
 No Ni, W 
 
 Waste Trt. Prob. 
 
 No Problem 
 
 Low Disaster Haz 
 
 Haz 
 
 Less Sludge 
 
 More 
 
 Recoverable 
 
 Recoverable 
 
 Possible Short Life 
 
 Long Life 
 
 Pollution Prevention 
 
 Substitution of a hard chromium plating solution eliminates hexavalent chromium from 
 the wastewater and air discharges of metal finishing facility. However, the alloy process 
 utilizes nickel and tungsten compounds which have also been linked to cancer. The net 
 effect is to replace one carcinogenic material with two that are possibly lesser . Since the 
 plating efficiency of the alloy process is only 24-35%, the process requires exhaust and 
 scrubbing to reduce air emissions. Air emissions regulations of nickel will most likely be 
 regulated under the Clean Air Act. EPA presently has no plans to regulate tungsten 
 emissions because little or no tungsten is currently used by the metal finishing industry. 
 Should the alloy process become popular, we would expect tungsten limitations on air, 
 water and land (RCRA) emissions. High concentrations of ammonium ions in the 
 wastewater stream would cause serious wastewater treatment problems due to chelatian 
 of metals such as copper and nickel. None of the ingredients in the alloy bath is an ^ 
 oxidant, so storage of the chemicals is simplified and the hazards of unwanted reactions 
 and explosions caused by accidental combination of oxidizer and reducing agent is 
 eliminated. 
 
 WORKER SAFETY/ECONOMICS: 
 Ni-W-SiC CHROMIUM 
 
 Draw???? 
 
 $$$$$ $ 
 
 Worker Safety/Economics 
 
 Worker safety is not significantly improved by the substitution of Ni-W-Si for chromium. 
 While hexavalent chromium is toxic and carcinogenic, nickel is also considered toxic and 
 carcinogenic. Tungsten compounds are listed as teratogens (birth defects). 
 
 Economic data on nickel-tungsten-silicon carbide is not available at this time. Considering 
 the difficulty in obtaining tungsten containing chemicals, it would be safe to assume the 
 cost would be much higher than for chromium plating. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 44 
 
Carbon for Electroless Copper 
 
 The circuit board industry is looking at a proprietary process that produces conductivity in 
 the thru-holes with carbon. The process uses conventional plating equipment and reduces 
 the number of processing tanks it takes to produce plated thru-holes. The process also 
 would eliminate the use of formaldehyde, which is a suspected carcinogen. 
 
 PROCESS DIFFERENCES: 
 
 CARBON 
 
 E'LESS COPPER 
 
 Prop. Conditioner 
 
 No 
 
 Prop. Cleaner 
 
 No 
 
 Alkaline 
 
 Also 
 
 Fine Carbon 
 
 Formaldehyde 
 
 (0.15 micron) 
 
 and Copper 
 
 Process Differences 
 
 The printed circuit boards are prepared prior to carbon coating in the same manner as for 
 electroless copper, including etch-back. Immediately prior to carbon coating, the boards 
 are processed through a proprietary cleaner and proprietary conditioning solutions which 
 are alkaline and contain weak complexing agents. The carbon coating solution is also 
 slightly alkaline and contains extremely fine carbon particles on the order of .15-.25 
 microns (6-10 millionths of an inch). The process has been commercially available since 
 1989 and is presently in use by many circuit board facilities. Suitability for plating on 
 plastics is unknown. 
 
 DEPOSIT DIFFERENCES: 
 CARBON ETESS COPPER 
 Thin Carbon Ctng.Thin Copper Ctng. 
 Good Adhesion Same 
 
 Good Therm Exp. Same 
 
 Deposit Differences 
 
 The carbon adsorbed onto the clean/etched surface of the circuit board can yield a 
 conductive surface that when copper plated compares favorably with electroless copper 
 in adhesive strength and thermal expansion characteristics. MIL-P-55110D permits the 
 use of this technology as a substitute for electroless copper. 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 45 
 
POLLUTION PREVENTION: 
 CARBON EULESS COPPER 
 No Chelates Chelates 
 
 No Formaldehyde Formaldehyde 
 No Heavy Metal Heavy Metal 
 Possible WT Prob. Also 
 
 Inc. COD Possibly same 
 Organic Collector No 
 
 Pollution Prevention/Regulatory Impact 
 
 Elimination of electroless copper removes a heavily chelated process from the wastewater 
 stream and at the same time, eliminates a carcinogenic material (formaldehyde) from use 
 in the shop. While it is unlikely to happen, finely divided carbon can react violently if 
 contacted with a strong oxidizer such as chromic acid. The suspended carbon may also 
 cause problems in wastewater treatment, by coating over probes, clogging filters, and 
 interfering with the proper operation of a clarifier. The carbon will not be removed by 
 conventional precipitation systems and needs to be controlled at the source. Carbon in 
 the wastewater discharge will significantly increase COD loading to the POTW. The 
 carbon may also act as an organic "collector", increasing Total Toxic Organic 
 concentrations in the wastewater discharge. Some POTWs have "excessive coloration" 
 regulations. Carbon containing discharges would probably fail to meet such regulations. 
 Plants using the carbon process and successfully controlling the above problems will 
 reduce the amount of solid/liquid waste generated. 
 
 WORKER SAFETY/ECONOMICS: 
 CARBON E'LESS COPPER 
 No Carcinogen Formaldehyde 
 
 Economics may be a draw 
 
 Worker Safety/Economics 
 
 Worker safety would be significantly improved by the elimination of formaldehyde from 
 the plating process. 
 
 Competitors using this process may have a competitive advantage by not have to waste 
 treat complexed copper by not using activation processes that contain palladium and tin 
 and by not generating as much solid waste for disposal. Added equipment for dealing 
 with the finely divided carbon may neutralize this economic advantage, however. 
 
 End Chapter 5 
 
 ® 1994, Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 46 
 
Appendix To Chapter V 
 
 Some Chemicals Used in the Metal Finishing Industry 
 
 
 pH 
 
 Cyanide 
 
 or 
 
 
 Chemical 
 
 adjustment 
 
 required 
 
 chromium 
 
 treatment 
 
 required 
 
 Waste products 
 
 Aluminum potassium sulfate 
 
 X 
 
 
 MS, DS 
 
 Aluminum silicate 
 
 X 
 
 
 MS, DS 
 
 Ammonium acetate 
 
 X 
 
 
 DS, NH3 
 
 Ammonium bifluoridee 
 
 X 
 
 
 MS DS, NH3 
 
 Ammonium chloride 
 
 X 
 
 
 DS, NH3 
 
 Ammonium citrate 
 
 X 
 
 
 DS NH3, 0 
 
 Ammonium hydroxide 
 
 X 
 
 
 DS, NH3 
 
 Ammonium molybdate 
 
 X 
 
 
 MS, DS, NH3 
 
 Ammonium nitrate 
 
 X 
 
 
 K, NH3 
 
 Ammonium sulfate 
 
 X 
 
 
 MS, DS, NH3 
 
 Anisic aldehyde 
 
 X 
 
 
 0 
 
 Antimony potassium tartrate 
 
 X 
 
 
 MS, DS, 0 
 
 Barium carbonate 
 
 X 
 
 
 MS 
 
 Barium sulfate 
 
 X 
 
 
 MS 
 
 Benzene (benzol) 
 
 X 
 
 
 0 
 
 Boric acid 
 
 X 
 
 
 DS 
 
 Cadmium cyanide 
 
 
 X 
 
 MS, DS 
 
 Cadmium sulfate 
 
 X 
 
 
 MS, DS 
 
 Calcium nitrate 
 
 X 
 
 
 DS 
 
 Chromic acid 
 
 
 X 
 
 MS, DS 
 
 Citric acid 
 
 X 
 
 
 DS,0 
 
 Cobalt carbonate 
 
 X 
 
 
 MS 
 
 Cobalt sulfate 
 
 X 
 
 
 MS, DS 
 
 Cupric sulfate 
 
 X 
 
 
 MS, DS 
 
 Diammonium phosphate 
 
 X 
 
 
 MS, DS, NH3 
 
 Ferric nitrate 
 
 X 
 
 
 MS, DS 
 
 Fluoboric acid 
 
 X 
 
 
 MS, DS 
 
 Formaldehyde 
 
 X 
 
 
 0 
 
 Glue 
 
 
 
 0 
 
 Glycerine 
 
 X 
 
 
 0 
 
 Hydrazine sulfate 
 
 X 
 
 
 DS 
 
 Hydrochloric acid CP 
 
 X 
 
 
 DS 
 
 Hydrofluosilicic 
 
 X 
 
 
 MS, DS 
 
 Hydrogen peroxide 
 
 X 
 
 
 
 Page 47 
 
pH 
 
 Chemical adjustment 
 
 required 
 
 Hydroxyacetic acid X 
 
 Hypophosphorus acid X 
 
 Indium sulfate X 
 
 Iron oxide X 
 
 Isopropanol X 
 
 Lard Oil 
 
 Lead Fluoborate X 
 
 Lead oxide X 
 
 Lime (calcium hydroxide) X 
 
 Magnesium sulfate X 
 
 Manganese carbonate X 
 
 Manganese sulfate X 
 
 Methanol X 
 
 Monoammonium phosphate X 
 
 Nickel carbonate X 
 
 Nickel chloride X 
 
 Nickel sulfate X 
 
 Nickel sulfamate X 
 
 Nitric Acid X 
 
 Oxalic acid X 
 
 Phosphorus acid X 
 
 Potasium bromate X 
 
 Potassium citrate X 
 
 Potassium chloride X 
 
 Potassium copper cyanide 
 Potassium cyanide 
 Potassium ferricyanide 
 Potassium hydroxide X 
 
 Potassium phosphate X 
 
 Potassium stannate X 
 
 Potassium thiocyanate X 
 
 Sodium acid pyrophosphate X 
 
 Soda ash (sodium carbonate) X 
 
 Sodium bicarbonate X 
 
 Sodium bisulfite X 
 
 Sodium bifluoride X 
 
 Sodium citrate X 
 
 Sodium copper cyanide 
 
 Cyanide 
 
 or 
 
 chromium 
 
 treatment 
 
 required 
 
 X 
 
 X 
 
 X 
 
 X 
 
 Waste products 
 
 DS, O 
 MS, DS 
 MS,DS 
 MS 
 0 
 0 
 
 MS,DS 
 
 MS 
 
 MS 
 
 MS, DS 
 MS 
 
 MS, DS 
 0 
 
 MS, DS, NH3 
 MS 
 
 MS, DS 
 
 MS, DS # 
 MS, DS 
 DS 
 
 MS, DS 
 MS, DS 
 DS 
 DS,0 
 DS 
 
 MS, DS 
 MS, DS 
 MS, DS 
 DS 
 DS 
 
 MS,DS 
 
 DS 
 
 MS, DS 
 DS 
 DS 
 DS 
 
 MS, DS 
 DS,0 
 
 MS, DS ^ 
 
 Page 48 
 
Chemical 
 
 pH 
 
 adjustment 
 
 Cyanide 
 
 or 
 
 chromium 
 
 Waste products 
 
 Sodium cyanide 
 
 required 
 
 treatment 
 
 required 
 
 X 
 
 . DS 
 
 Sodium dichromate 
 
 
 X 
 
 MS, DS 
 
 Sodium fluoborate 
 
 
 X 
 
 MS, DS 
 
 Sodium gluconate 
 
 
 X 
 
 DS 
 
 Sodium hexametaphosphate 
 
 X 
 
 
 MS, DS 
 
 Sodium hypophosphite 
 
 X 
 
 
 MS, DS 
 
 Sodium Hydrosulfite 
 
 X 
 
 
 DS 
 
 Sodium hydroxide (caustic soda) 
 
 X 
 
 
 DS 
 
 Sodium metasilicate 
 
 X 
 
 
 MS, DS 
 
 Sodium molybdate 
 
 X 
 
 
 MS, DS 
 
 Sodium nitrate 
 
 X 
 
 
 DS 
 
 Sodium orthosilicate 
 
 X 
 
 
 MS,DS 
 
 Sodium polysulfide 
 
 X 
 
 
 MS, DS 
 
 Sodium stannate 
 
 X 
 
 
 MS, DS 
 
 Sodium sulfate 
 
 X 
 
 
 DS 
 
 Sodium sulfide 
 
 X 
 
 
 MS,DS 
 
 Sodium sulfite 
 
 X 
 
 
 DS 
 
 Sodium tripolyphosphate 
 
 X 
 
 
 MS, DS 
 
 Stannous fluoborate 
 
 X 
 
 
 MS, DS 
 
 Stannous sulfate 
 
 X 
 
 
 MS, DS 
 
 Stearic acid 
 
 X 
 
 
 0 
 
 Sulfamic acid 
 
 X 
 
 
 DS 
 
 Sulfur (Liquid) 
 
 X 
 
 
 MS 
 
 Sulfuric acid 
 
 X 
 
 
 MS, DS 
 
 Tallow givceride 
 
 X 
 
 
 0 
 
 Tartaric acid 
 
 X 
 
 
 0 
 
 Tetrapotassium pyrophosphate 
 
 X 
 
 
 MS, DS 
 
 Tetrasodium pyrophosphate 
 
 X 
 
 
 MS,DS 
 
 Toluene (Toluol) 
 
 Trichlorethylene 
 
 Trichloroethane 
 
 Trisodium phosphate 
 
 X 
 
 
 0 
 
 0 
 
 0 
 
 MS, DS 
 
 Xylene (Xylol) 
 
 Zinc chloride 
 
 X 
 
 
 0 
 
 MS,DS 
 
 Zinc cyanide 
 
 
 X 
 
 MS, DS 
 
 MS = metal sludge; NH3 = ammonia; DS = dissolved solids; O = organic matter. 
 
 Page 49 
 
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Table of Contents 
 
 VI. Key Drivers and Barriers to Pollution Prevention 
 
 in Metal Finishing 
 
 Topic Page Number 
 
 EPA survey of industry 1 
 
 Listing of Hazardous Waste 2 
 
 Mixture/Derived-from Rule 2 
 
 Metal Finishing Standards (New source) 3 
 
 Superfund, Joint and Several Liability Provisions 4 
 

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Part VI, KEY DRIVERS AND BARRIERS TO 
 POLLUTION PREVENTION IN 
 METAL FINISHING 
 
 Tier 1: Top Firms, pride in industry 
 Tier 2: Maintain regulatory compliance 
 Tier 3: Older outdated facilities 
 Tier 4: Renegade, non-compliance 
 
 Inconsistency due to uncertainty 
 
 A recent survey conducted by USEPA concluded that drivers and barriers to pollution 
 prevention vary for different "tiers" in the metal finishing industry: 
 
 Tier 1; These are top firms, driven by recognition and pride in industry performance. They 
 see the economic payoffs of strategic environmental investments. They maximize 
 flexibility in compliance and promote innovative approaches and willingness to share 
 knowledge in pollution prevention methods. 
 
 Tier 2: These firms are driven mainly by the need to maintain regulatory compliance. 
 Barrier to pro-active performance include lack of capital, information, positive 
 reenforcement, and a non-level playing field created by lack of uniform enforcement on 
 their competitors. Many facilities at this level are heavily dependent upon their suppliers 
 for methods of pollution prevention. 
 
 Tier 3: These are older, outdated facilities that have a strong fear of liability under 
 Environmental regulations and find it difficult to improve due to lack of capital, 
 knowledge, and floor space. 
 
 Tier 4: These are "renegade" facilities that compete at an unfair advantage gained 
 through non-compliance with environmental regulations. The facilities may be "hidden" 
 and un-reported, or may be going through an appearance of compliance. 
 
 Inconsistency among regulatory requirements and enforcement actions at federal, state, 
 and local levels creates a major barrier in advancing pollution prevention, due to the 
 "uncertainty" factor about upcoming or modified regulations that might render a major 
 investment unusable or problematic. Uncertainty also makes long range planning difficult 
 or impossible. 
 
 Some regulatory provisions are in themselves significant barriers to pollution prevention in 
 this industry: 
 
 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 1 
 
Listing of Hazardous Waste 
 
 * F-006 RCRA, 40 CFR part 261 
 
 * Need viable method of proving non-hazardous status 
 
 Mixture/Derived From Rule 
 
 * RCRA, 40CFR part 261.3 (a) (2) (iv) 
 
 * Inhibits recycling of hazardous waste 
 
 Listing of Hazardous Waste (F-006) (RCRA. 40CFR part 261) 
 
 The waste generated from the wastewater pretreatment system from an electroplating 
 operation is a hazardous waste due to listing (there are very few exemptions, such as 
 waste from pretreatment of rinsewater from non-cyanide zinc electroplating on ferrous 
 substrates). There are provisions in the regulations for "delisting" a hazardous waste, but 
 the procedures are extremely expensive and time consuming. The generated waste, in 
 many cases, would not meet the listing criteria and theoretically would meet non- 
 hazardous status, if ERA created a procedure for determining whether a metal finishing 
 waste meets the listing criteria. Until such time occurs, metal finishing facilities appear to 
 be generating large volume of "hazardous" waste simply because no viable method of ^ 
 proving its non-hazardous status is available. 
 
 Mixture/Derived From Rate (RCRA. 40CFR part 261.3 (a) 12) (iv)) 
 
 This provision of the RCRA regulations effectively causes any mixture of hazardous waste 
 with non-hazardous materials to be come a hazardous waste in total. Further, any 
 material derived from a hazardous waste is also considered hazardous. Even if the waste 
 or product derived from the waste is treated or is inherently non-hazardous, there is no 
 "out". This provision has been successfully challenged in court, but ERA is enforcing it on 
 an interim basis, while it seeks to develop methods of defining a hazardous waste. In the 
 meantime, this RCRA provision inhibits recycling of hazardous waste, except by a few 
 companies who have spent the large sums of money necessary to "delist" their by 
 products from recycled hazardous waste. It also drives the cost of disposing recyclable 
 waste up and creates recycling opportunities only for the facilities that can afford to send 
 the waste to such recycling firms (all of which are located outside the state of Illinois, 
 except for one facility, Recontek, located in Illinois, but very limited in capability. 
 
 Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 2 
 
Meta! Finishing Standards (CWA. 40CFR part 433) 
 
 In the promulgation of the metal finishing standards, EPA stated their intent to move 
 existing job shop electroplaters from 40CFR part 413 regulation to regulation under part 
 433. The difference between the two standards is significant: 
 
 PRETREATMENT STANDARDS (mg/L) 
 
 Job Shops; Metal Finishers: 
 
 Pollutant; 
 
 1 Day M 
 
 ax 4 Day Avo 
 
 1 Day Max 
 
 30 Day Avg 
 
 Cadmium 
 
 1.2 
 
 0.7 
 
 0.69* 
 
 0.26* 
 
 Chromium 
 
 7.0 
 
 4.0 
 
 2.77 
 
 1.71 
 
 Copper 
 
 4.5 
 
 2.7 
 
 3.38 
 
 2.07 
 
 Lead 
 
 0.6 
 
 0.4 
 
 0.69 
 
 0.43 
 
 Nickel 
 
 4.1 
 
 2.6 
 
 2.61 
 
 1.48 
 
 Silver 
 
 — 
 
 — 
 
 0.43 
 
 0.24 
 
 Zinc 
 
 4.2 
 
 2.6 
 
 2.61 
 
 1.48 
 
 Cyanide-T 
 
 1.9 
 
 1.0 
 
 1.2 
 
 0.65 
 
 TTO 
 
 2.13 
 
 (grab) 
 
 2.13 
 
 (grab) 
 
 pH 
 
 — 
 
 6-9 
 
 6-9 
 
 Cu-H Zn-}-Cr-l-Ni 10.5 
 
 6.8 
 
 — 
 
 — 
 
 (Total Metals) 
 
 Above are the most commonly applied sewer discharge regulations. Note that job shops 
 have in general, higher limitations than metal finishers. * 
 
 We should also note that new source metal finishers must meet regulated Cadmium 
 discharge levels at 0.1 Img/L 1 Day max and 0.07 mg/L 30 Day Avg. Also, the cyanide 
 limits for metal finishers must be complied with at the point of treatment (as opposed to 
 the end of pipe for job shop metal finishers). 
 
 An existing job shop electroplating facility risks the re-classification into new source metal 
 finishing category, if it invests the money necessary to relocate, or to tear down an older 
 processing line and replace it with a modern line incorporating modern pollution 
 prevention methods. 
 
 In several cities, POTWs have interpreted major renovations to pretreatment systems as 
 sufficient modernization to re-classify the shop in the metal finishing category! 
 
 Such misinterpretations of the intent of the federal regulations are counterproductive, as 
 an existing facility will tend to resist modernizing, in an effort to maintain their existing 
 discharge category. 
 
 Federal guidance as to what constitutes enough change to re-categorize a facility is 
 needed. 
 
 ® Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 3 
 
Superfund. Joint and Several Liability Provisions 
 
 * Discontinue / liquidate 
 
 * Cautious Lenders 
 
 * Harmful Government Specs 
 
 * Break-in period - violations 
 
 * "Charlatan" saviors 
 
 * Cross media effects 
 
 * Hesitant attitude - history, knowledge 
 
 Superfund. Joint and Several Liability Provisions 
 
 A number of metal finishing firms face significant environmental liabilities and clean-up 
 costs, if they discontinue operations and attempt to liquidate their assets. This potential 
 liability creates the double "whammy" of creating a barrier to exit for these firms and 
 effectively eliminating access to capital for improvements. 
 
 Liability provisions under Superfund, that hold lenders of capital liable, in the event of a 
 Superfund clean-up at a metal finishing facility, causes lenders to be extremely cautious in 
 providing necessary capital for metal finishers to improve their operations and install 
 pollution prevention methods. 
 
 Other barriers to pollution prevention include: 
 
 The embarrassing tendency of governmental defense agencies to continue to specify 
 environmentally harmful coatings to be applied to military components, even when less 
 harmful alternates are available. 
 
 There is a concern about the "break-in" period that normally is required after a pollution 
 prevention device or technique is installed. Invariably, the "learning curve" will cause a 
 violation of a local or state regulation, as an operating parameter is refined or if the 
 equipment breaks down. The resulting violation acts as a deterrent to the installation of the 
 device. 
 
 The industry has seen many "charlatan" saviors, who profess to have all the answers in 
 their little "black box". Poor experiences and lost capital expended on such devices has 
 created an aura of suspicion about any new technology that enters the market. 
 
 Cross media effects can also inhibit pollution prevention, as when an improved method for 
 scrubbing air emissions ends up creating more scrubbant waste to treat, and at higher ^ 
 concentrations than before. 
 
 © Frank Altmayer, Scientific Control Labs. Inc. 
 
 Page 4 
 
A considerable lack of history and control knowledge about substitute "cleaner" 
 processes creates a hesitant attitude about investing in a substitute process. 
 
 There is considerable concern about recycling methods contaminating the process the 
 recycling method is installed on, causing the entire process solution to be sent off site for 
 treatment/disposal. It is not un-common for a metal finishing process solution to cost 
 $15.00/gallon to make-up (some solutions are as high as $30.00/gal and precious metals 
 plating solutions can cost thousands of dollars per gallon). By recycling rinsewater to 
 such processes (as opposed to treating), the concern is that in the long term the recycling 
 method will contaminate the process beyond salvageability and therefore create more 
 waste than was saved. 
 
 ® Frank Altmayer, Scientific Control Labs. Inc 
 
 Page 5 
 
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