630.7 
 I6b 
 
 no. 676 
 cop. 8 
 
UNIVERSITY OF 
 
 ILLINOIS LIBRARY 
 
 AT URBANA-CHAMPAIGN 
 
 AGRICULTURE 
 

 
^ 
 
 = u 
 
 BULLETIN 676 
 
 10 -YEAR PAINT 
 WEATHERED GALVANIZED ROOFING 
 
 By A. J. Muehling and J. O. Curtis 
 
 UNIVERSITY OF ILLINOIS 
 AGRICULTURAL EXPERIMENT STATION 
 
Urbana, Illinois August, 1961 
 
 Publications in the Bulletin series report the results of investigations made 
 or sponsored by the Experiment Station 
 
' 
 
 
 CONTENTS 
 
 DESCRIPTION OF TESTS 6 
 
 Application of Paints 6 
 
 Inspections 13 
 
 Criteria for Evaluating Tests 13 
 
 TEST RESULTS 15 
 
 Performance of Paint Systems 15 
 
 Effect of Exposure 20 
 
 Effect of Original Condition of Sheet 22 
 
 Effect of Wire Brushing Sheets Before Applying Paint 23 
 
 SUMMARY 26 
 
 LITERATURE CITATIONS. . . .27 
 
 COVER PHOTO fhe 150-foot corn crib on which the paint study 
 was conducted (south side after application of first coat of paint). 
 
This bulletin was prepared by A. J. Muehling and J. O. 
 Curtis, Assistant Professors of Agricultural Engineering. 
 
 The research reported here was initiated by R. W. 
 Whitaker, formerly Instructor of Agricultural Engineering, 
 now Director of Agricultural Research, A. O. Smith Cor- 
 poration, Milwaukee, under the direction of D. G. Carter, 
 Professor of Agricultural Engineering. 
 
 For several years, inspections of the test panels were 
 conducted in the Department by H. L. Wakeland, now 
 Assistant Dean of the College of Engineering, University 
 of Illinois. 
 
 Funds for this project were provided in part by the 
 American Zinc Institute and the Aluminum Company of 
 America. 
 
GALVANIZED METAL SHEETS ARE STEEL SHEETS that have been COated 
 with zinc to prevent the steel from rusting. As this zinc coating 
 deteriorates through weathering, the steel becomes exposed and begins 
 to rust. Besides being unsightly, rusting reduces the life of the roofing. 
 
 Galvanized metal roofing and siding are used extensively on farm 
 buildings. A 1941-1942 survey (8)* by the American Zinc Institute 
 in 36 states east of the Rocky mountains showed that one-third of all 
 farm buildings had galvanized steel roofs. More than one-fourth of 
 these roofs were rusty. According to a 1944-1954 survey (7), the 
 roofs of about one-half of all Illinois farm buildings were made of 
 galvanized steel. About 50 percent of these roofs showed signs of rust. 
 
 The application of protective paints is one of the least expensive 
 means of preventing rusting of galvanized metal sheets, provided that 
 the paint is chosen carefully. Painting also makes the building more 
 attractive and can reduce roof temperatures by reflection. 
 
 Paints vary in their ability to adhere to metals, to withstand ex- 
 posure, and to prevent rusting. Manufacturers' tests indicate the rela- 
 tive ability of paints to protect metal from corrosion. However, the 
 final evaluation of a particular paint can be obtained only by direct 
 exposure to the elements. According to several authorities (5, 10) 
 accelerated laboratory tests do not predict the service life of a paint, 
 and the final trial should be under field conditions. 
 
 In 1932, the American Zinc Institute established tests of paints on 
 galvanized metal roofs at Donnellson, Illinois. These tests are usually 
 referred to as the Harwood Tests. In 1948, test data covering 16 years 
 were turned over to the Department of Agricultural Engineering at 
 the University of Illinois. The data were analyzed and the results 
 published (3,4). 
 
 After studying the results of the Harwood Tests and reviewing 
 other technical literature on paint for metal roofs, the University of 
 
 * This number and similar numbers in parentheses refer to the literature 
 citations on page 27. 
 
6 BULLETIN NO. 676 
 
 Illinois Department of Agricultural Engineering initiated a new series 
 of paint tests in June, 1949. This project was supported in part with 
 funds supplied by the American Zinc Institute and the Aluminum 
 Company of America. 
 
 The objective of these tests was to expand the knowledge gained 
 from the Harwood Tests. Information was sought concerning (a) the 
 durability of metallic zinc paints for priming and finish coats on rusty 
 galvanized metal roofing; (b) the durability of aluminum paints as 
 finish coats over various primers; and (c) the value of wire brushing 
 the rusty surface before painting. 
 
 The roof of a 150-foot crib on one of the University-owned Aller- 
 ton farms near Monticello, Illinois, was chosen for the tests (see 
 cover photo). The rural location corresponded to the least severe 
 ordinary exposure condition, according to the classification of atmos- 
 pheric types used by the American Society for Testing Materials (11). 
 The condition of the galvanized sheets on this roof did not vary as 
 much as the condition of the sheets used in the Harwood Tests. Much 
 of the metal was quite rusty. A trace of black asphalt paint remained 
 on most sheets from a previous painting. These surface conditions were 
 as severe as one would be likely to encounter in farm buildings. 
 
 DESCRIPTION OF TESTS 
 
 Application of Paints 
 
 Each panel was composed of corrugated metal sheets approxi- 
 mately 2 feet wide and extending up one side of the crib and down the 
 other. This arrangement gave a north and south exposure for each 
 panel. Before painting, all panels were renailed where needed, and 
 the entire roof was brushed with a broom to remove all loose foreign 
 material. A three-foot strip of roof was wire brushed across the 
 northern exposure of panels 46 through 81 to evaluate the practice of 
 wire brushing a rusty galvanized sheet before painting. 
 
 Twenty-three paints from 11 manufacturers were hand-sprayed on 
 the test panels in 7 one-coat and 34 two-coat applications. Replications 
 were made of all but two panels (panels 11 and 16). In addition to 
 giving better test data, these replications provided some insurance 
 against a complete loss of record in the event that some of the sheets 
 were blown off the roof. Fig. 1 shows the numbered panels on the crib 
 and lists the paint combinations that were tested. The compositions of 
 the paints as reported by the manufacturers are listed in Table 1. 
 
FIRST COAT 
 
 1 GRAY MZP (SOYBEAN OIL) 
 
 2 GRAY MZP (SOYBEAN OIL) 
 
 3 ZINC CHROMATE PRIMER 
 
 4 ZINC CHROMATE-IRON OXIDE 
 
 5 RED LEAD (LINSEED OIL) 
 
 6 WHITE LEAD 
 
 7 RED MZP 
 
 8 RED MZP 
 
 9 IRON OXIDE (RED RUST-RESISTING PAINT) 
 
 10 GREEN MZP 
 
 11 GREEN MZP 
 
 12 GREEN AUTO ENAMEL 
 
 13 GRAY MZP (LINSEED OIL) 
 
 14 RED LEAD (LINSEED OIL) 
 
 15 RED LEAD (SEMI-QUICK-DRYING VEHICLE) 
 
 16 ZINC CHROMATE-IRON OXIDE 
 
 17 ZINC CHROMATE PRIMER 
 
 18 ALUMINUM, GENERAL PURPOSE (I) 
 
 19 ALUMINUM, GENERAL PURPOSE (I) 
 
 20 GRAY MZP (SOYBEAN OIL) 
 
 21 GRAY MZP (SOYBEAN OIL) 
 
 22 GRAY MZP (SOYBEAN OIL) 
 
 23 GRAY MZP (LINSEED OIL) 
 
 24 GRAY MZP PRIMER 
 
 25 RED LEAD OXIDE (LINSEED OIL) 
 
 26 GRAY MZP PRIMER 
 
 27 ALUMINUM (RUST-RESISTING VEHICLE) 
 
 28 ALUMINUM (RUST-RESISTING VEHICLE) 
 
 29 RED LEAD OXIDE (LINSEED OIL) 
 
 30 GRAY MZP (SOYBEAN OIL) 
 
 31 GRAY MZP (SOYBEAN OIL) 
 
 32 ASPHALT ALUMINUM 
 
 33 ASPHALT ALUMINUM 
 
 34 ASBESTOS ASPHALT 
 
 35 ALUMINUM, FOR METAL & MASONRY (I) 
 
 36 ALUMINUM, FOR METAL & MASONRY (I) 
 
 37 ALUMINUM, SPECIAL 
 
 38 GRAY MZP (SOYBEAN OIL) 
 
 39 GRAY MZP (SOYBEAN OIL) 
 
 40 GRAY MZP (SOYBEAN OIL) 
 
 41 SPECIAL RED PRIMER (NORTH ONLY) 
 
 42 GRAY MZP (SOYBEAN OIL) 
 
 43 GRAY MZP (SOYBEAN OIL) 
 
 44 ZINC CHROMATE PRIMER 
 
 45 ZINC CHROMATE-IRON OXIDE 
 
 46 RED LEAD (LINSEED OIL) 
 
 47 WHITE LEAD 
 
 48 RED MZP 
 
 49 RED MZP 
 
 50 IRON OXIDE (RED RUST-RESISTING PAINT) 
 
 51 GREEN MZP 
 
 52 GREEN MZP 
 
 53 GREEN AUTO ENAMEL 
 
 54 GREEN MZP (LINSEED OIL) 
 
 55 RED LEAD (LINSEED OIL) 
 
 56 RED LEAD (SEMI-QUICK-DRYING VEHICLE) 
 
 57 SPECIAL RED PRIMER 
 
 58 ZINC CHROMATE PRIMER 
 
 59 ALUMINUM, GENERAL PURPOSE (I) 
 
 60 ALUMINUM, GENERAL PURPOSE (I) 
 
 61 GRAY MZP (SOYBEAN OIL) 
 
 62 GRAY MZP (SOYBEAN OIL) 
 
 63 GRAY MZP (SOYBEAN OIL) 
 
 64 GRAY MZP (LINSEED OIL) 
 
 65 GRAY MZP PRIMER 
 
 66 RED LEAD OXIDE (LINSEED OIL) 
 
 67 GRAY MZP PRIMER 
 
 68 ALUMINUM (RUST-RESISTING VEHICLE) 
 
 69 ALUMINUM (RUST-RESISTING VEHICLE) 
 
 70 RED LEAD OXIDE (LINSEED OIL) 
 
 71 GRAY MZP (SOYBEAN OIL) 
 
 72 GRAY MZP (SOYBEAN OIL) 
 
 73 ASPHALT ALUMINUM 
 
 74 ASPHALT ALUMINUM 
 
 75 ASBESTOS ASPHALT 
 
 76 ALUMINUM, FOR METAL & MASONRY (I) 
 
 77 ALUMINUM, FOR METAL & MASONRY (I) 
 
 78 ALUMINUM, SPECIAL 
 
 79 GRAY MZP (SOYBEAN OIL) 
 
 80 GRAY MZP (SOYBEAN OIL) 
 
 81 GRAY MZP (SOYBEAN OIL) 
 
 SECOND COAT 
 
 GRAPHITE 
 
 RED MZP 
 
 RED MZP 
 
 RED MZP 
 
 RED MZP 
 
 RED MZP 
 
 RED MZP 
 
 NONE 
 
 IRON OXIDE (RED RUST-RESISTING PAINT) 
 
 NONE 
 
 GREEN AUTO ENAMEL 
 
 GREEN MZP 
 
 ALUMINUM, FOR METAL & MASONRY (I) 
 
 ALUMINUM, FOR METAL & MASONRY (I) 
 
 ALUMINUM, FOR METAL & MASONRY (I) 
 
 ALUMINUM, FOR METAL & MASONRY (I) 
 
 ALUMINUM, FOR METAL & MASONRY (I) 
 
 NONE 
 
 ALUMINUM, GENERAL PURPOSE (I) 
 
 ALUMINUM, FOR METAL & MASONRY (I) 
 
 ALUMINUM, GENERAL PURPOSE (II) 
 
 ALUMINUM (RUST-RESISTING VEHICLE) 
 
 ALUMINUM (RUST-RESISTING VEHICLE) 
 
 ALUMINUM (RUST-RESISTING VEHICLE) 
 
 ALUMINUM (RUST-RESISTING VEHICLE) 
 
 ALUMINUM, GENERAL PURPOSE (II) 
 
 NONE 
 
 ALUMINUM (RUST-RESISTING VEHICLE) 
 
 ALUMINUM, FOR METAL & MASONRY (II) 
 
 ALUMINUM, FOR METAL & MASONRY (II) 
 
 ASPHALT ALUMINUM 
 
 ASPHALT ALUMINUM 
 
 NONE 
 
 ASPHALT ALUMINUM 
 
 NONE 
 
 ALUMINUM, FOR METAL & MASONRY (I) 
 
 ALUMINUM, SPECIAL 
 
 ALUMINUM, GENERAL PURPOSE (I) 
 
 NONE 
 
 GRAY MZP (SOYBEAN OIL) 
 
 GRAY MZP (SOYBEAN OIL) (NORTH ONLY) 
 
 GRAPHITE 
 
 RED MZP 
 
 RED MZP 
 
 RED MZP 
 
 RED MZP 
 
 RED MZP 
 
 RED MZP 
 
 NONE 
 
 IRON OXIDE (RED RUST-RESISTING PAINT) 
 
 NONE 
 
 GREEN MZP 
 
 GREEN MZP 
 
 ALUMINUM, FOR METAL & MASONRY (I) 
 
 ALUMINUM, FOR METAL & MASONRY (I) 
 
 ALUMINUM, FOR MFTAL & MASONRY (I) 
 
 ALUMINUM, FOR METAL & MASONRY (I) 
 
 ALUMINUM, FOR METAL & MASONRY (I) 
 
 NONE 
 
 ALUMINUM, GENERAL PURPOSE (I) 
 
 ALUMINUM, FOR METAL & MASONRY (I) 
 
 ALUMINUM, GENERAL PURPOSE (II) 
 
 ALUMINUM (RUST-RESISTING VEHICLE) 
 
 ALUMINUM (RUST-RESISTING VEHICLE) 
 
 ALUMINUM (RUST-RESISTING VEHICLE) 
 
 ALUMINUM (RUST-RESISTING VEHICLE) 
 
 ALUMINUM, GENERAL PURPOSE (II) 
 
 NONE 
 
 ALUMINUM (RUST-RESISTING VEHICLE) 
 
 ALUMINUM, FOR METAL & MASONRY (II) 
 
 ALUMINUM, FOR METAL & MASONRY (II) 
 
 ASPHALT ALUMINUM 
 
 ASPHALT ALUMINUM 
 
 NONE 
 
 ASPHALT ALUMINUM 
 
 NONE 
 
 ALUMINUM, FOR METAL & MASONRY (I) 
 
 ALUMINUM, SPECIAL 
 
 ALUMINUM, GENERAL PURPOSE (I) 
 
 NONE 
 
 GRAY MZP (SOYBEAN OIL) 
 
 Paint treatment for each panel of the corn-crib roof used in the tests. (Fig. 1 ) 
 
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10 BULLETIN NO. 676 [August, 
 
 ASTM standards D 1014-51 (11) was followed as closely as pos- 
 sible when setting up the test procedure. Singleton (9) states that 
 when making paint tests, the description of a painting system must 
 include at least three items: (a) the condition of the steel surface 
 when it is painted, (b) the paint composition, and (c) the thickness 
 of paint or amount of paint used on a given area. 
 
 Excellent colored slides showing the original condition of the panels 
 were taken before the tests began. These slides were studied and the 
 amount of rust on each panel was recorded (see pages 16 to 18). The 
 condition of the panels before painting can be seen in Fig. 2. 
 
 Paint was hand-sprayed on the panels in consecutive order, start- 
 ing with the first panel on the west end of the building. All paint was 
 applied according to the manufacturers' directions by the same person 
 using the same equipment. 
 
 The paint coatings were applied with a small (0.203 gallon) De- 
 Vilbiss pressure cup unit. An aluminum shield was used to prevent 
 the spray from blowing to adjacent panels (Fig. 3). The sprayer cup 
 was cleaned after each application except when the same paint was 
 applied to successive panels. Panels that were to have the same paint 
 were grouped together to reduce the time and labor required for wash- 
 ing the cup and maneuvering the shield. 
 
 Table 2 shows the amount of paint applied to each panel, weight 
 per gallon, and the amount of coverage in square feet per gallon of 
 each paint used. The values from Table 2 were determined by the 
 following procedure: 
 
 1. The cup was filled to the 0.203-gallon capacity and weighed 
 before the test panel was painted. 
 
 2. After the panel was painted, the weight of the cup was recorded. 
 
 3. The weight of the cup was subtracted from the full weight to 
 obtain the pounds of paint applied. 
 
 4. Weight per gallon was calculated from the full weight of the 
 cup, the known empty weight of the cup unit (3.43 pounds), and the 
 known capacity of the cup (0.203 gallon). 
 
 Full weight minus empty weight (3.43 pounds) equals actual 
 
 weight of 0.203 gallon of paint. 
 
 Weight per gallon equals 1/0.203 times actual weight of 0.203 
 
 gallon of paint. 
 
 The weight per gallon for a given paint sometimes varied slightly 
 because of variation in mixing and in the quantity of thinner used (if 
 any) . See footnote b under Table 2 for paints thinned. 
 
?96J] 
 
 PAINT TESTS ON GALVANIZED ROOFING 
 
 11 
 
 North side of crib before painting. The one-third of the roof at the left (Panels 46 through 
 81) was 100 percent rusty. (Fig. 2) 
 
 5. The gallons used per panel were calculated by dividing the 
 weight of paint used per panel by the weight per gallon. 
 
 6. The actual areas for each panel were measured. 
 
 The coverage in square feet per gallon was calculated by dividing 
 the panel area by the gallons used on the panel. 
 
 When the same paint was applied to successive panels, they were 
 painted as a single unit and separate panel calculations were not made. 
 
 An aluminum shield was used to prevent spray from blowing to adjacent panels. (Fig. 3) 
 
12 
 
 BULLETIN NO. 676 
 
 [August, 
 
 Table 2. Area of Panels, Quantities of Paint Used, and Paint Coverage 
 
 Panel 
 No. 
 
 Panel 
 area 
 (square 
 feet) 
 
 First coat 
 
 Second coat 
 
 Paint 
 No. 
 
 Amount 
 of paint 
 used 
 (pounds) 
 
 Weight Coverage 
 per (square 
 gallon feet per 
 (pounds) gallon) 
 
 Paint 
 No. 
 
 Amount 
 of paint 
 used 
 (pounds) 
 
 Weight 
 per 
 gallon 
 (pounds) 
 
 Coverage 
 
 (square 
 feet per 
 gallon) 
 
 1 
 
 . 80.4 
 
 1 
 1 
 4 
 5 
 6 
 7 
 3 
 3 
 8 
 9 
 9 
 10 
 11 
 6 
 13 
 5 
 4 
 14 
 14 
 1 
 1 
 1 
 11 
 16 
 18 
 16 
 17 
 17 
 18 
 1 
 1 
 20 
 20 
 21 
 12 
 12 
 22 
 1 
 1 
 1 
 
 23 
 1 
 1 
 4 
 5 
 6 
 7 
 3 
 3 
 8 
 9 
 9 
 10 
 11 
 6 
 
 3.48 
 3.02 
 2.60 
 2.08 
 5.25 
 3.45 
 2.88 
 2.66 
 2.39 
 4.01 
 4.12 
 2.25 
 4.79 
 7.30 
 4.93 
 2.58 
 4.38 
 1.47 
 1.47 
 4.90 
 4.90 
 4.90 
 4.48 
 4.25 
 2.57 
 4.33 
 1.31 
 1.31 
 3.01 
 3.83 
 3.83 
 1.22 
 1.22 
 7 pints 
 1.32 
 1.32 
 1.03 
 3.55 
 3.50 
 3.19 
 0.81 
 3.36 
 3.55 
 2.16 
 2.26 
 7.52 
 4.59 
 3.36 
 3.36 
 2.72 
 4.20 
 4.20 
 2.24 
 4.90 
 6.00 
 
 22.0 
 22.0 
 14.4 
 11.4 
 31.1 
 18.6 
 16.2 
 16.2 
 11.7 
 17.7 
 17.7 
 8.1 
 25.0 
 28.2 
 24.2 
 11.5 
 14.5 
 7.7 
 7.7 
 22.6 
 22.6 
 22.6 
 24.3 
 24.3 
 13.3 
 24.5 
 8.1 
 8.1 
 13.3 
 22.5 
 22.5 
 8.1 
 8.1 
 unknown 
 8.5 
 8.5 
 7.7 
 23.5 
 23.5 
 23.5 
 9.4 
 23.5 
 23.5 
 14.5 
 12.6 
 38.6 
 22.3 
 16.2 
 16.2 
 12.1 
 23.5 
 23.5 
 8.6 
 25.9 
 35.6 
 
 510 
 
 510 
 410 
 405 
 425 
 390 
 415 
 415 
 325 
 315 
 315 
 270 
 405 
 290 
 370 
 340 
 250 
 395 
 395 
 350 
 350 
 350 
 410 
 390 
 345 
 405 
 470 
 470 
 335 
 445 
 445 
 505 
 505 
 85 
 490 
 490 
 565 
 505 
 505 
 505 
 385 
 505 
 505 
 510 
 425 
 390 
 370 
 365 
 365 
 340 
 425 
 425 
 290 
 400 
 435 
 
 2 
 3 
 3 
 3 
 3 
 3 
 3 
 
 8 
 
 10 
 9 
 12 
 12 
 12 
 12 
 12 
 
 14 
 12 
 15 
 17 
 17 
 17 
 17 
 15 
 
 17 
 19 
 19 
 20 
 20 
 
 20 
 
 12 
 22 
 14 
 
 1 
 1 
 2 
 3 
 3 
 3 
 3 
 3 
 3 
 
 8 
 
 9 
 9 
 12 
 12 
 
 3.06 
 2.89 
 3.07 
 3.07 
 2.99 
 2.98 
 3.07 
 
 11.6 
 
 17.7 
 17.7 
 17.7 
 17.7 
 17.7 
 17.7 
 
 305 
 
 425 
 425 
 425 
 425 
 425 
 425 
 
 2 
 
 ... 69.8 
 
 3 
 
 ... 74.0 
 
 4 
 
 ... 74.0 
 
 5b 
 
 ... 72.2 
 
 6. . 
 
 71.9 
 
 7 
 
 74.0 
 
 8 
 
 ... 68.4 
 
 9 
 
 . . . 66.6 
 
 1.95 
 
 12.0 
 
 410 
 
 10 
 
 . . . 71 .8 
 
 11 
 
 . . 74.0 
 
 2.25 
 2.35 
 1 .50 
 1 .45 
 1.45 
 1.45 
 1.45 
 
 8.3 
 
 18.7 
 7.9 
 7.9 
 7.9 
 7.9 
 7.9 
 
 275 
 600 
 410 
 410 
 410 
 410 
 410 
 
 12 
 
 ... 76.0 
 
 13 . .. 
 
 78.2 
 
 14 b 
 
 ... 76.0 
 
 15 
 
 ... 76.0 
 
 16 b 
 
 76.0 
 
 17 
 
 .. 76.0 
 
 18 
 
 ... 76.0 
 
 19 
 
 76.0 
 
 1.40 
 1.00 
 1.10 
 1.50 
 1.50 
 1.35 
 1.32 
 1.10 
 
 7.9 
 7.9 
 7.6 
 8.1 
 
 8.1 
 8.1 
 8.1 
 7.4 
 
 430 
 600 
 525 
 410 
 410 
 410 
 410 
 480 
 
 20 
 
 ... 76.0 
 
 21 
 
 ... 76.0 
 
 22 
 
 ... 76.0 
 
 23 
 
 76.0 
 
 24 
 
 .. 68.4 
 
 25 
 
 ... 66.6 
 
 26. . 
 
 . 71.8 
 
 27 
 
 . 76.0 
 
 28 
 
 ... 76.0 
 
 1.40 
 1.38 
 1.38 
 1.20 
 1.20 
 
 7.6 
 8.6 
 8.6 
 8.3 
 8.3 
 
 415 
 
 475 
 475 
 525 
 525 
 
 29 
 
 ... 76.0 
 
 30 
 
 . 76.0 
 
 31 
 
 .. 76.0 
 
 32 
 
 ... 76.0 
 
 33 
 
 76 
 
 34 
 
 . 76.0 
 
 1.20 
 
 8.3 
 
 525 
 
 35 
 
 ... 76.0 
 
 36... 
 
 76.0 
 
 1.30 
 1.35 
 1.35 
 
 8.8 
 8.3 
 8.3 
 
 515 
 465 
 465 
 
 37 
 
 76 
 
 38 
 
 76.0 
 
 39 
 
 ... 75.2 
 
 40 
 
 68 4 
 
 4.00 
 1.95 
 2.80 
 2.86 
 2.86 
 2.86 
 2.86 
 2.86 
 2.86 
 
 23.8 
 23.8 
 11.3 
 18.4 
 18.4 
 18.4 
 18.4 
 18.4 
 18.4 
 
 405 
 405 
 290 
 490 
 490 
 490 
 490 
 490 
 490 
 
 41... 
 
 . 33.3 
 
 42 
 
 .. 72.3 
 
 43 
 
 ... 76.0 
 
 44 
 
 76 
 
 45 b 
 
 ... 76.0 
 
 46>>... 
 
 76.0 
 
 47 
 
 ... 76.0 
 
 48 
 
 76 
 
 49 b 
 
 ... 76.0 
 
 50 . . 
 
 76 
 
 2.60 
 
 13.5 
 
 395 
 
 51. . 
 
 76 
 
 52 
 
 ... 76.0 
 
 2.95 
 2.95 
 1.35 
 1.30 
 
 20.9 
 20.9 
 8.6 
 8.6 
 
 540 
 540 
 485 
 485 
 
 53. . 
 
 ... 76.0 
 
 54. . 
 
 76 
 
 55>> 
 
 ... 73.5 
 
 
 
 A detailed description of the paints is given in Table 1. 
 b The following paints were thinned to obtain better spraying consistency: 
 Panel 5 Red lead (linseed oil) 12 ounces of turpentine added to 9.08 pounds of 
 
 red lead. 
 Panel 14 Red lead (linseed oil) 2 ounces of turpentine added to 7.70 pounds of 
 
 red lead. Mixed more thoroughly than for Panel 5. 
 Panels 16 and 45 Zinc chromate-iron oxide 3 ounces of turpentine added to 5.77 
 
 pounds of paint. 
 Panels 46 and 55 Red lead (linseed oil) 6yi ounces of turpentine added to 18.5 
 
 pounds of paint. About 5 ounces of linseed oil added to paint for Panel 55. 
 Panel 49 Red MZP 1 ounce of turpentine added to 1 cup of paint. 
 c Only the north side of Panel 41 was painted. A new galvanized sheet was placed on the 
 southern exposure before the paint tests started. 
 
J96JJ 
 
 PAINT TESTS ON GALVANIZED ROOFING 
 
 Table 2. Concluded 
 
 13 
 
 Panel 
 
 No. 
 
 Panel 
 area 
 (square 
 feet) 
 
 First coat 
 
 Second coat 
 
 Paint 
 No. 
 
 Amount 
 of paint 
 used 
 (pounds) 
 
 Weight Coverage 
 per (square 
 gallon feet per 
 (pounds) gallon) 
 
 Amount 
 Paint of paint 
 No. used 
 (pounds) 
 
 Weight 
 per 
 gallon 
 (pounds) 
 
 Coverage 
 
 (scjuaic 
 feet per 
 gallon) 
 
 56 . 
 
 . 66.6 
 
 13 
 23 
 4 
 14 
 14 
 1 
 1 
 1 
 11 
 16 
 18 
 16 
 17 
 17 
 18 
 1 
 1 
 20 
 20 
 21 
 12 
 12 
 22 
 1 
 1 
 1 
 
 4.90 
 1.40 
 2.55 
 1 .20 
 1.20 
 3.32 
 3.32 
 3.32 
 4.25 
 4.45 
 2.65 
 4.25 
 1.12 
 1.12 
 3.55 
 3.70 
 3.34 
 1.14 
 1 .26 
 7 pints 
 1.30 
 1 .30 
 1.00 
 3.70 
 3.70 
 4.00 
 
 25.7 
 8.6 
 14.4 
 8.0 
 8.0 
 23.5 
 23.5 
 23.5 
 26.7 
 25.2 
 13.4 
 25.7 
 8.7 
 8.7 
 13.7 
 24.1 
 24.1 
 8.6 
 8.6 
 unknown 
 8.5 
 8.5 
 8.2 
 24.6 
 24.6 
 24.6 
 
 350 
 415 
 420 
 505 
 505 
 535 
 535 
 535 
 480 
 430 
 385 
 460 
 590 
 590 
 295 
 480 
 480 
 500 
 500 
 85 
 485 
 485 
 625 
 505 
 505 
 505 
 
 12 
 12 
 12 
 
 14 
 12 
 15 
 17 
 17 
 17 
 17 
 15 
 
 17 
 19 
 19 
 20 
 20 
 
 20 
 
 12 
 22 
 14 
 
 1 ' 
 
 .18 
 .20 
 .32 
 
 '.45 
 .25 
 .50 
 .29 
 .29 
 .29 
 .29 
 .30 
 
 8.6 
 8.6 
 8.6 
 
 8.6 
 8.3 
 8.3 
 8.2 
 8.2 
 8.2 
 8.2 
 9.3 
 
 485 
 485 
 485 
 
 450 
 
 500 
 420 
 485 
 485 
 485 
 485 
 540 
 
 57 
 
 . 67.6 
 
 58 
 
 74.1 
 
 59 
 
 ... 76.0 
 
 60 
 
 76.0 
 
 61 . 
 
 76.0 
 
 62 
 
 76 
 
 63 
 
 76.0 
 
 64 
 
 ... 76.0 
 
 65 
 
 76 
 
 66 
 
 76 
 
 67 
 
 . . 76.0 
 
 68 
 
 76.0 
 
 69 
 
 76.0 
 
 .45 
 .30 
 .26 
 .74 
 
 .74 
 
 9.1 
 8.3 
 8.3 
 7.7 
 7.7 
 
 480 
 485 
 485 
 690 
 690 
 
 70 
 
 ... 76.0 
 
 71 . . 
 
 73.6 
 
 72 
 
 66 6 
 
 73. . 
 
 . 66.4 
 
 74. . 
 
 ... 72.8 
 
 75 
 
 ... 74.0 
 
 .83 
 
 1 '.55 
 .35 
 .50 
 
 7.7 
 
 's'.i 
 
 8.1 
 8.1 
 
 690 
 
 385 
 455 
 410 
 
 76. . 
 
 74.0 
 
 77 
 
 74 
 
 78 ... 
 
 76.2 
 
 79. . 
 
 ... 76.2 
 
 80 
 
 ... 76.2 
 
 81 .. 
 
 82.6 
 
 L10 
 
 24.8 
 
 500 
 
 
 
 These panels were painted without using the shield or cleaning the cup 
 after painting each panel. Average values are given for successive 
 panels when the same paint was used. 
 
 Inspections 
 
 Inspections were made each year (1950 through 1959, with the 
 exception of 1955) by members of the Farm Structures Division of 
 the Department of Agricultural Engineering. Since most of the in- 
 spectors worked with the project four years in succession, they de- 
 veloped proficiency in judging the panels. The yearly inspections were 
 made by the inspectors viewing each panel from a platform at eave 
 height. A high platform was built over a pickup truck so that it could 
 be moved along the eaves as the inspections were made. Each panel 
 was studied and the percent of film failure was recorded. The north 
 and south exposures were inspected separately. 
 
 Criteria for Evaluating Tests 
 
 An important consideration in evaluating paint tests is to select an 
 objective method for determining the life of a paint system. Browne 
 (2) lists people in four categories according to their use of paint as 
 
14 
 
 BULLETIN NO. 676 
 
 [August, 
 
 those who (a) paint for appearance; (b) paint when the film shows 
 signs of failing but is not badly deteriorated; (c) paint long after the 
 surface should have been painted; and (d) do not paint at all. 
 
 Obviously, each of these groups has a different idea of when the 
 "repaint stage" is reached. To evaluate paint tests, the repaint stage 
 must be defined. Singleton (9) states that "To the larger body of 
 technical men who are paint users rather than paint makers, panel tests 
 are only incidental. These men are concerned with the cost and the 
 quality of protection that the paint will give on structures in service. 
 The goal of panel testing should be not merely to compare different 
 paint combinations, but to determine the life of the paint on the struc- 
 ture. The results should be a quantitative figure representing the life 
 of the paint system in months or years to a stage where repainting is 
 necessary." 
 
 One way to define repaint stage is to compare the condition of a 
 panel with the ASTM photographic standards (12) as adopted in 1943 
 and reapproved without change in 1958. Numerous authorities (Sin- 
 gleton, Walton, Burgener) have recommended ASTM No. 8 as the 
 stage in the photographic standards when repainting is necessary 
 (Fig. 4). This standard corresponds to a film failure of about 5 per- 
 cent (4). For comparison of paint performance in this test, 5-percent 
 film failure was used as the repaint stage. All panels did not reach 
 5-percent film failure or repaint stage during the 10-year test period. 
 
 Photographic reference standard Number 8 type 1, rusting not accompanied by blister- 
 ing. This standard has often been recommended as the "repaint stage." Photo courtesy 
 American Society for Testing Materials. (See literature citation 12.) (Fig. 4) 
 
7967] PAINT TESTS ON GALVANIZED ROOFING 15 
 
 TEST RESULTS 
 
 Performance of Paint Systems 
 
 The paint-performance data for all paint systems are summarized 
 in Table 3. The average percent film- failure ratings are listed for the 
 9 inspections (1949 to 1959, with the exception of 1955). The percent 
 film-failure rating is an estimate of the percent of total area of the 
 panel where the paint film failed and rust occurred. The southern and 
 northern exposures of each panel were graded separately. Since the 
 panels had one replication, the film- failure values listed in the table 
 are an average for two panels. For the sake of convenience, any film 
 failure below 1 percent was coded as 0.5 percent. 
 
 The relative durability of each paint system is shown by the "time 
 to repaint stage." This stage represents the approximate time at which 
 5 percent of the surface of the test panel was devoid of paint. In the 
 two-coat systems, the degree of failure applied to both coats of paint. 
 A number of paint systems did not have a film failure of 5 percent at 
 the end of 10 years and, therefore, did not reach repaint stage. 
 
 Table 4 lists the 15 paint systems with the smallest percent of film 
 failure after 10 years' exposure. Since most of the panels did not 
 reach repaint stage in 10 years, the paints were ranked according to 
 the average percent film failure at that time. The last four paint sys- 
 tems reached the repaint stage before the end of 10 years. 
 
 The aluminum paints used as a second coat over red lead or gray 
 MZP (Metallic Zinc Paint) gave the best overall performance. All of 
 the panels painted a first coat of red lead and a second coat of one of 
 the aluminum paints (other than asphalt aluminum) performed well. 
 A large number of the panels painted with a base coat of gray MZP and 
 a second coat of one of the aluminum paints did not reach repaint stage 
 after 10 years' exposure. The panels with two coats of gray MZP were 
 nearing repaint stage at the end of 10 years. 
 
 Table 5 summarizes the results of all one-coat paint systems and 
 all paint systems composed of two coats of the same paint. In the one- 
 coat paint systems, the performance of red MZP and gray MZP was 
 about the same. Each gave approximately 5 years' protection before 
 repaint stage. All single-coat paint systems of MZP gave a better 
 performance than single coats of aluminum paint. 
 
 When two applications of the same paint were used, gray MZP 
 (soybean oil, paint No. 1) gave the best performance over 10 years' 
 protection. The paint system composed of two coats of aluminum 
 (paint No. 12, aluminum for metal and masonry) protected the panel 
 for over 8 years before repaint stage was reached. 
 
16 
 
 BULLETIN NO. 676 
 
 [August, 
 
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 PAINT TESTS ON GALVANIZED ROOFING 
 
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18 
 
 BULLETIN NO. 676 
 
 [August, 
 
 
 
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796?] 
 
 PAINT TESTS ON GALVANIZED ROOFING 
 
 19 
 
 Table 4. Performance of Paint Systems With Smallest Percent 
 of Film Failure 
 
 Rank 
 
 Paint 
 system 
 
 Paint 
 No." 
 (first 
 coat) 
 
 Paint 
 No." 
 (second 
 coat) 
 
 Film failure at 10 years, percent 
 
 Southern 
 exposure 6 
 
 Northern 
 exposure 1 ' 
 
 Average 
 
 1.. 
 
 29 
 
 18 
 18 
 
 1 
 11 
 1 
 1 
 1 
 5 
 1 
 16 
 12 
 13 
 1 
 4 
 3 
 
 19 
 17 
 14 
 12 
 19 
 12 
 15 
 12 
 1 
 15 
 12 
 12 
 3 
 12 
 3 
 
 .25 
 .50 
 1.75 
 2.50 
 5.00 
 3.50 
 4.50 
 6.00 
 5.00 
 2.50 
 3.00 
 2.50 
 13.50 
 3.50 
 14.00 
 
 2.50 
 2.75 
 3.00 
 2.25 
 .50 
 2.75 
 3.00 
 3.00 
 4.25 
 7.00 
 6.50 
 10.00 
 
 10.50 
 1.00 
 
 1.38 
 1.62 
 2.38 
 2.38 
 2.75 
 3.12 
 3.75 
 4.50 
 4.62 
 4.75 
 4.75 
 6.25 d 
 6.75 d 
 7.00 d 
 7.50 d 
 
 2 
 
 25 
 
 3 
 
 38 
 
 4 
 
 ... 13 
 
 5 
 
 ... 30 
 
 6 
 
 20 
 
 7 
 
 21 
 
 8 
 
 16a 
 
 9 
 
 40 
 
 10 
 
 26 
 
 11 
 
 36 
 
 12 
 
 15 
 
 13 
 
 2 
 
 14 
 
 17 
 
 15 
 
 7 
 
 
 
 A detailed description of the paints is given in Table 1. 
 b Except for Paint System 16a, all values are the average of two panels. 
 c Film-failure value is for only one panel. See footnote g, Table 3. 
 d Reached repaint stage before the end of 10 years. 
 
 Table 5. Performance of One-Coat Paint Systems and Paint Systems 
 With Two Coats of the Same Paint 
 
 Rank 
 
 Paint 
 system 
 
 Paint 
 No." 
 
 Film failure at 10 years, 
 
 percent 
 
 Time to 
 repaint 
 stage 
 (years) 
 
 Southern 
 exposure 6 
 
 Northern 
 exposure 6 
 
 Average 
 
 1.. 
 
 8 
 
 One-coat paint 
 3 38.5 
 1 15.0 
 9 48.5 
 14 90.0 
 12 47.5 
 17 87.5 
 20 87.5 
 
 Two-coat paint 
 1 5.0 
 12 3.0 
 3 14.0 
 17 5.0 
 9 17. O d 
 20 24.5 
 14 21.0 
 8 47.5 
 22 57.5 
 
 systems 
 13.00 
 29.00 
 25.00 
 70.00 
 53.50 
 80.00 
 92.50 
 
 systems 
 4.25 
 6.50 
 1.00 
 11.00 
 5.00 d 
 44.00 
 19.00 
 46.00 
 52.00 
 
 28.50 
 22.00 
 36.80 
 80.00 
 50.50 
 83.80 
 90.00 
 
 4.62 
 4.75 
 7.50 
 8.00 
 11.00 
 34.25 
 20.00 
 46.50 
 54.75 
 
 sy 2 
 
 5 
 3 
 1 
 
 1 A 
 1 A 
 
 y 2 
 
 over 10 
 over S^2 
 over 8 
 
 lYi 
 7H 
 4', 
 
 4 
 4 
 2 
 
 2 
 
 39 
 
 3 
 
 10 
 
 4 
 
 18 
 
 5 
 
 35 
 
 6 
 
 ... 27 
 
 7 
 
 33 
 
 1.. 
 
 40 
 
 2 
 
 36 
 
 3 
 
 7 
 
 4 
 
 28 
 
 5 
 
 lib 
 
 6.. 
 
 32 
 
 7 
 
 19 
 
 8 
 
 9 
 
 9 
 
 37 
 
 
 
 A detailed description of the paints is given in Table 1. 
 
 b Except for Paint System lib, all values are the average of two panels. 
 
 c Values were calculated to the nearest one-half year. 
 
 d Film-failure value is for only one panel. See footnote f, Table 3. 
 
20 
 
 BULLETIN NO. 676 
 
 [August, 
 
 Table 6 summarizes the results of all paint systems that had a base 
 coat of gray MZP. In general, the paint systems that had an alumi- 
 num paint top coat over a gray MZP base coat again gave the best 
 performances. 
 
 Table 6. Performance of Paint Systems With Gray MZP Base Coat 
 
 Rank 
 
 Paint 
 system 
 
 Paint 
 No. a 
 (first 
 coat) 
 
 Paint 
 No. a 
 (second 
 coat) 
 
 Film failure at 10 years, percent 
 
 Time to 
 repaint 
 stage 
 (years) 
 
 Southern 
 exposure 11 
 
 Northern 
 exposure 11 
 
 Average 
 
 1 
 
 38 
 
 1 
 11 
 1 
 1 
 1 
 1 
 16 
 1 
 1 
 16 
 11 
 1 
 1 
 
 14 
 12 
 12 
 15 
 19 
 1 
 15 
 3 
 17 
 17 
 17 
 20 
 2 
 
 1.75 
 2.50 
 3.50 
 4.50 
 5.00 
 5.00 
 2.50 
 13.50 
 9.50 
 17.50 
 13.00 
 12.50 
 17.00 
 
 3.00 
 
 2.25 
 2.75 
 3.00 
 .50 
 4.25 
 7.00 
 
 7.50 
 7.75 
 8.50 
 9.00 
 11.00 
 
 2.37 
 2.37 
 3.12 
 3.75 
 2.75 
 4.62 
 4.70 
 6.75 
 8.50 
 12.62 
 10.75 
 10.75 
 14.00 
 
 over 10 
 over 10 
 over 10 
 over 10 
 over 10 
 over 10 
 over 9 
 over 8 
 7 
 6H 
 6H 
 6 
 4^ 
 
 2 
 
 . . 13 
 
 3 
 
 20 
 
 4.. 
 
 . . . 21 
 
 5 
 
 ... 30 
 
 6 
 
 .. . 40 
 
 7 
 
 . .. 26 
 
 8 . . . 
 
 2 
 
 9 
 
 . 22 
 
 10 
 
 24 
 
 11 
 
 . .. 23 
 
 12 
 
 .. . 31 
 
 13 
 
 1 
 
 
 
 A detailed description of the paints is given in Table 1. 
 
 b All values are the average of two panels. 
 
 c Values were calculated to the nearest one-half year. 
 
 Figs. 5 through 8 show the performance over the 10-year period 
 of the metallic zinc paints, the aluminum paints, all paint systems with 
 a gray MZP base coat, and all paint systems with red lead, white lead, 
 or zinc chromate for the base coat, respectively. All values on these 
 graphs are averages for north and south exposures. 
 
 Effect of Exposure 
 
 Exposure had an appreciable effect on the performance of the red 
 and green paints, but no apparent effect on the paint systems with an 
 aluminum paint top coat. Table 7 summarizes the 10-year performance 
 of all paint systems with a red or green top coat and all paints with 
 an aluminum paint top coat. 
 
 In every case, the film failures from the paint systems with a red 
 or green top coat were larger for the southern exposure than for the 
 northern exposure. The exposure did not seem to affect the perform- 
 ance of the paint systems that had a second coat of one of the aluminum 
 paints. Fig. 9 shows the contrast between the two groups of paints. 
 The average film failures at 10 years were almost equal (20.3 compared 
 with 22.0) for the northern and southern exposures of the paint systems 
 
J96J] PAINT TESTS ON GALVANIZED ROOFING 21 
 
 Table 7. Effect of Southern and Northern Exposures 
 on Paint Performance 
 
 Film failure at 
 
 Paint 
 
 Paint No." 
 
 Paint No. 
 
 10 years, 
 
 percent 
 
 system 
 
 (first coat) 
 
 (second coat) 
 
 Southern 
 
 Northern 
 
 
 
 
 exposure 6 
 
 exposure 6 
 
 Paint systems with red and green 
 
 top coats 
 
 
 2 
 
 1 
 
 3 
 
 13.50 
 
 
 
 3 
 
 4 
 
 3 
 
 23.50 
 
 .25 
 
 4 
 
 5 
 
 3 
 
 55.00 
 
 7.50 
 
 5 
 
 6 
 
 3 
 
 53.50 
 
 9.00 
 
 6 
 
 7 
 
 3 
 
 25.00 
 
 3.00 
 
 7 
 
 3 
 
 3 
 
 14.00 
 
 1.00 
 
 8 
 
 3 
 
 none 
 
 38.50 
 
 13.00 
 
 10 
 
 9 
 
 none 
 
 48.50 
 
 25.00 
 
 lla 
 
 9 
 
 10 
 
 55.00" 
 
 1.00 
 
 lib 
 
 9 
 
 9 
 
 17. 00 
 
 5.00 
 
 12 
 
 10 
 
 9 
 
 22.50 
 
 8.75 
 
 Average. ... 
 
 
 
 34.50 
 
 9.90 
 
 Paint systems with aluminum top 
 
 coats 
 
 
 13 
 
 11 
 
 12 
 
 2.50 
 
 2.25 
 
 14 
 
 6 
 
 12 
 
 3.50 
 
 17.00 
 
 15 
 
 13 
 
 12 
 
 2.50 
 
 10.00 
 
 16a 
 
 5 
 
 12 
 
 6.00" 
 
 3.00' 
 
 16b 
 
 23 
 
 12 
 
 4.00" 
 
 65.00 C 
 
 17 
 
 4 
 
 12 
 
 3.00 
 
 10.50 
 
 18 
 
 14 
 
 none 
 
 90.00 
 
 70.50 
 
 19 ... 
 
 14 
 
 14 
 
 21.00 
 
 19.50 
 
 20 
 
 1 
 
 12 
 
 3.50 
 
 2.75 
 
 21 
 
 1 
 
 15 
 
 4.50 
 
 3.00 
 
 22 
 
 1 
 
 17 
 
 9.50 
 
 7.50 
 
 23 
 
 11 
 
 17 
 
 13.00 
 
 8.50 
 
 24 
 
 16 
 
 17 
 
 17.50 
 
 7.75 
 
 25 
 
 18 
 
 17 
 
 .25 
 
 .50 
 
 26 
 
 16 
 
 15 
 
 2.50 
 
 7.00 
 
 27 
 
 17 
 
 none 
 
 87.50 
 
 80.00 
 
 28 
 
 17 
 
 17 
 
 5.00 
 
 11 50 
 
 29 
 
 18 
 
 19 
 
 .25 
 
 2.50 
 
 30 
 
 1 
 
 19 
 
 5.00 
 
 .50 
 
 31 
 
 1 
 
 20 
 
 12.50 
 
 9.00 
 
 32 
 
 20 
 
 20 
 
 24.50 
 
 44.00 
 
 33 
 
 20 
 
 none 
 
 87.50 
 
 92.50 
 
 34 
 
 21 
 
 20 
 
 33.50 
 
 5.50 
 
 35 
 
 12 
 
 none 
 
 47.50 
 
 53.50 
 
 36 
 
 12 
 
 12 
 
 3.00 
 
 6.50 
 
 37 
 
 22 
 
 22 
 
 57.50 
 
 52.50 
 
 38 
 
 1 
 
 14 
 
 1.75 
 
 3.00 
 
 Average. ... 
 
 
 
 20.30 
 
 22.00 
 
 * A detailed description of the paints is given in Table 1. 
 
 b Except for Paint Systems lla, lib, 16a, and 16b, all values are the average of two panels. 
 
 c Film-failure values are for only one panel. See footnotes f and g, Table 3. 
 
22 
 
 BULLETIN NO. 676 
 
 [August, 
 
 that had an aluminum second coat. There was a large difference, how- 
 ever (34.5 compared with 9.9), between paint systems with a second 
 coat of red or green paint. The kind of exposure did not seem to affect 
 the performance of the gray MZP. 
 
 Effect of Original Condition of Sheet 
 
 The original condition of the metal sheets on the test crib varied 
 from 45 to 100 percent rusty (see Table 3). 
 
 The panels on the northern exposure for the second replication 
 were 100 percent rusty when they were painted, and the average film 
 failure at the end of 10 years was 28.4 percent. The panels for the 
 first replication on the northern exposure varied from 50 to 90 percent 
 rusty, with an average of 65 percent rusty, and the average film failure 
 
 PAINT SYSTEMS 
 
 (TWO COATS) 
 
 (TWO COATS) o 
 
 (TWO COATS) o 
 
 (ONE COAT) 
 
 (ONE COAT) 
 
 (ONE COAT) 
 
 40 - GRAY MZP 
 
 7 - RED MZP 
 lib - GREEN MZP 
 39 - GRAY MZP 
 
 8 - RED MZP 
 10 - GREEN MZP 
 
 234567 
 
 EXPOSURE TIME IN YEARS 
 
 Performance of metallic zinc paints. 
 
 (Fig. 5) 
 
?96I] 
 
 PAINT TESTS ON GALVANIZED ROOFING 
 
 23 
 
 PAINT SYSTEMS 
 
 36 - AL.FOR METAL t MASONRY(I) (TWO COATS) 
 28 - AL (RUST- RESISTING VEHICLE) (TWO COATS) 
 
 34 - ASBESTOS ASPHALT (111 COAT) 
 
 ASPHALT AL (2<tf COAT) 
 
 19 - AL. GENERAL PURPOSE (I) (TWO COATS) 
 
 32 - ASPHALT ALUMINUM (TWO COATS) 
 
 35 - AL.FOR METAL t MASONRY (I) (ONE COAT) 
 37- AL, SPECIAL (TWO COATS) 
 18- AL. GENERAL PURPOSE (I) (ONE COAT) 
 27 - AL (RUST-RESISTING VEHICLEKONE COAT) 
 
 33 - ASPHALT ALUMINUM (ONE COAT) 
 
 23456 
 EXPOSURE TIME IN YEARS 
 
 7 8 9 10 
 
 Performance of aluminum paints. 
 
 at the end of 10 years was only 7.8 percent. The difference between 
 these two averages indicates that the original condition of the panels 
 had a definite effect on the performance of the paint systems. 
 
 Effect of Wire Brushing Sheets Before Applying Paint 
 
 One of the objectives of this test was to evaluate the practice of 
 brushing a rusty galvanized sheet before applying paint. In prepara- 
 tion for painting, all of the panels were swept with a broom to remove 
 all foreign material. 
 
 The top portions of the bottom sheets of panels 46 through 81 on 
 the northern exposure were wire brushed before painting (Fig. 10). 
 These sheets were inspected each year. During the tenth yearly in- 
 
24 
 
 BULLETIN NO. 676 
 
 [Aogojf, 
 
 spection, panels 46 through 81 were studied with special care to see 
 if any difference existed between the paint performance of the sections 
 that had been wire brushed and the remaining portions of the panels. 
 As far as could be determined, the wire brushing had no effect on the 
 ability of the paint to withstand weathering. 
 
 This conclusion agrees with the rinding of Walton (13). After a 
 7-year paint study at Pennsylvania State University, Walton stated 
 that "In preparing a rusty steel roof for painting, it is unnecessary to 
 wire brush the surface to free it of rusty particles. It will be sufficient 
 to whisk the surface free of loose particles of foreign matter." 
 Matthews (8) also observed that steel brushing was unnecessary in 
 the preparation of rusty galvanized sheets for painting. 
 
 PAINT SYSTEMS 
 
 SECOND COAT 
 
 1 3 - GRAY 
 38 -GRAY 
 30 -GRAY 
 20- GRAY 
 
 2 I - GRAY 
 40 -GRAY 
 26 -GRAY 
 
 2 -GRAY 
 22 -GRAY 
 
 3 I - GRAY 
 23- GRAY 
 24 GRAY 
 
 I - GRAY 
 39 - GRAY 
 
 MZP (LINSEED OIL) 
 MZP (SOYBEAN OIL) 
 MZP (SOYBEAN OIL) 
 MZP (SOYBEAN OIL) 
 MZP (SOYBEAN OIL) 
 MZP (SOYBEAN OIL) 
 MZP PRIMER 
 MZP (SOYBEAN OIL) 
 MZP (SOYBEAN OIL) 
 MZP (SOYBEAN OIL) 
 MZP (LINSEED OIL) 
 MZP PRIMER 
 MZP (SOYBEAN OIL) 
 MZP (SOYBEAN OK.) 
 
 AL, FOR METAL C MASONRY (I) 
 
 AL, GENERAL PURPOSE (I) 
 
 AL, TOR METAL $ MASONRY IE) 
 
 AL, FOR METAL 6 MASONRY (I) 
 
 AL, GENERAL PURPOSE (D) 
 
 GRAY MZP (SOYBEAN OIL) 
 
 AL, GENERAL PURPOSE (H) 
 
 RED MZP 
 
 AL (RUST- RESISTING VEHICLE) 
 
 ASPHALT ALUMINUM 
 
 AL (RUST- RESISTING VEHICLE) 
 
 AL (RUST- RESISTING VEHICLE) 
 
 GRAPHITE 
 
 NONE 
 
 3456 
 EXPOSURE TIME IN YEARS 
 
 Performance of paint systems with gray MZP for a first coat. 
 
 (Fig. 7) 
 
J967] 
 
 PAINT TESTS ON GALVANIZED ROOFING 
 
 25 
 
 SYSTEMS 
 
 SECOND COAT 
 
 29-RED LEAD OXIDE (LINSEED OIL) 
 35 -RED LEAD OXIDE (LINSEED OIL) 
 160-ZNC CHROMATE-IRON OXIDE 
 15-RED LEAD (SEMI-OUICK-DRYING 
 
 VEHICLE) 
 
 17- ZINC CHROMATE PRIMER 
 14- RED LEAD (LINSEED OIL) 
 
 3- ZINC CHROMATE PRIMER 
 6- WHITE LEAD 
 
 5- RED LEAD (LINSEED OIL) 
 
 4- ZINC CHROMATE-IRON OXDE 
 
 AL, FOR METAL 4 MASONRY (H) 
 AL (RUST-RESISTING VEHICLE) 
 AL, FOR METAL t MASONRY (I) -- 
 AL, FOR METAL t MASONRY (I) 
 
 AL. FOR METAL t MASONRY (I) 
 AL, FOR METAL $ MASONRY (I) 
 RED MZP - 
 
 RED MZP 
 
 RED MZP 
 
 EXPOSURE TIME IN YEARS 
 
 Performance of paint systems with red lead, white lead, or zinc chromate for a first coat. 
 
 (Fig. 8) 
 
 RED AND GREEN TOP COATS 
 
 ALUMINUM TOP COATS 
 
 5 10 15 20 25 30 35 
 
 AVERAGE PERCENT OF FILM FAILURE AT THE END OF 10 YEARS 
 
 Effect of exposure on red and green top coats and aluminum top coats (Fig. 9) 
 
26 
 
 BULLETIN NO. 676 
 
 [August, 
 
 The top portions of the bottom sheets of Panels 46 through 81 on the north side were 
 wire brushed before painting. These panels were 100 percent rusty (see Fig. 2). (Fig. 10) 
 
 SUMMARY 
 
 Among the general conclusions drawn from this study, the follow- 
 ing are most significant. 
 
 1. Exposure had a definite effect on the paint systems with a red 
 or green top coat, but no apparent effect on the paint systems with an 
 aluminum top coat. All panels with a paint system composed of a red 
 or green top coat had an appreciably larger film failure on the southern 
 exposure than on the northern exposure. There was no significant 
 difference between film failures on the northern and southern ex- 
 posures for the aluminum top coats, or for the gray MZP top coat. 
 
 2. The original condition of the panel affected the amount of pro- 
 tection offered by the paint system. The greater the amount of rust 
 when the panel was painted, the faster the paint film failed. 
 
 3. The paint systems that provided the best protection were those 
 with a first coat of red lead and a second coat of an aluminum paint 
 and those with a first coat of gray metallic zinc paint and a second 
 coat of an aluminum paint. 
 
 4. Wire brushing before painting gave no apparent increased pro- 
 tection to the panels. If the panels had not been brushed, however, 
 more paint would have been necessary to secure a good coverage. 
 
J96J] PAINT TESTS ON GALVANIZED ROOFING 27 
 
 LITERATURE CITATIONS 
 
 1. BARTELLS, G. C. Test results of metallic zinc paint on galvanized sheet metal. 
 
 Agr. Engin. 20:101-103. 1939. 
 
 2. BROWNE, F. L. Testing house paints for durability. U. S. Dept. Agr. Forest 
 
 Prod. Lab., Madison, Wis. 
 
 3. BURGENER, M. L., and CARTER, D. G. Protective coatings for weathered gal- 
 
 vanized sheets. Agr. Engin. 31:67-70. 1950. 
 
 4. BURGENER, M. L., and CARTER, D. G. Durability of paints on weathered gal- 
 
 vanized roofing. 111. Agr. Exp. Sta. Bui. 565. 16p. 1953. 
 
 5. EVANS, U. R. Metallic corrosion passivity and protection. Edward Arnold 
 
 and Co. London. 720p. 1938. 
 
 6. HOCKER, C. D. Outdoor test results on bare and metal-coated ferrous speci- 
 
 mens. Symposium on the outdoor weathering of metals and metallic 
 coatings, pp. 1-19. Regional meeting ASTM, Washington, D. C. 1934. 
 
 7. IRISH, W. W. Illinois farm building activities and trends, 1944-1954. Un- 
 
 published Master's thesis. Univ. of 111. 1955. 
 
 8. MATTHEWS, C. A. Spray painting farm metal roofs. Agr. Engin. 29:542-544. 
 
 1948. 
 
 9. SINGLETON, W. F. The interpretation of visual rusting standards. Proc. 
 
 ASTM 44:910-915. 1944. 
 
 10. SPELLER, F. N. Corrosion, causes and prevention. McGraw-Hill. New York. 
 
 686p. 3d ed. 1951. 
 
 11. Standard method of conducting exterior exposure tests of paint on steel 
 
 (D1014-51). ASTM Standards 8:846-874. 1958. 
 
 12. Standard method of evaluating degree of resistance to rusting obtained with 
 
 paint on iron and steel surfaces (D610-43). ASTM Standards 8:875-880. 
 1958. 
 
 13. WALTON, H. V. Painting galvanized steel roofing: exposure studies. Pa. 
 
 Agr. Exp. Sta. Prog. Rpt. 139. lip. 1955. 
 
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