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Materiah of Construction Review
Protective Coatings by Francis Scofield, National Paint, Varnish, and Lacquer Association, Washington, D. C.
Pre fin ished bu if d in g- co m po n e n ts assure better initial coatings D U R I N G THE PAST YEAR, there has been no single development in the paint industry which has dominated the field. Probably the most significant single trend has been the growing realization that the problem of achieving a satisfactory coated surface is not simply one of cnoosing the correct coating but is a complex process, often starting with the design of the structure to be coated and carrying on through surface preparation, application, and curing. Each of these facets must be considered with the others in mind, as well as with thought of the exposure to be encountered and the results desired. Certainly, it is becoming widely recognized that the “best” paint for one set of conditions (design, surface preparation, application, and curing conditions, among others) is not, necessarily, or even probably, the best paint for another set of conditions. When this situation is combined with the flood of new materials which are becoming available, as well as the improved forms of older materials, obviously much more work on evaluating the interaction of these various factors must be done if intelligent choices among various alternatives are to be made. A great deal of work is going on. The influence of all these variables has stimulated much interest in factory finishing of building components, where some of these variables may be controlled. This should, in the future: assure better initial coatings than can be obtained at this time by field application but will not solve maintenance problems. For this, the variables of field application must still be considered. The review period covered is essentially the calendar year 1960.
N e w e r Materials I t requires considerable time and work to determine the place of new raw materials in the general scheme of protective coatings. During the past year two relatively new types of coating have shown considerable promise-polyesters and urethanes. I n particular, these coatings appear to have a place in one of the most difficult areas in the coating field, clear coatings for exterior wood.
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Gray ( 6 4 has reported on a number of comparative exposures, emphasizing the difficulties inherent in getting satisfactory service. The general properties of polyester coatings were discussed by Bardin (3A) and Kostiuk ( 7 2 A ) , and Allan ( 7 A ) covered their application to wood finishes, especially. Hampton and others (8A), Knaf (77A), and Patton (75A) described the general properties of various types of urethane coatings, and McGinnis (73A) and Wells (2UA) emphasized their use as clear coatings for wood. As with all new materials, time is required to evaluate these materials, but there is promise that coatings with better durability will be available for exterior wood. Epoxy coatings are somewhat older, and their place in the coatings field is a little better defined. The emphasis now is on their use in specific fields. Howard and others (70A) reviewed their use in petroleum refineries, and Elliott and Dickson (5A) described their use for protecting metals from corrosion. Vinyl resins continue to be very helpful for metal coatings, since their high chemical resistance is very useful. I n particular, the use of dispersionsorganosols and plastisols-which permit the application of heavier coatings, has continued to increase. Guffie ( 7 A ) has outlined some recent advances in this field, and other reviews (74A, 7G.4) covered other applications. Among other raw materials used as materials of construction are the fluorinecontaining polymers. The low solubility of these materials in conventional paint solvents has prevented their application for many purposes, but expedients to avoid this difficulty are being developed. Banks and Haszeldine ( 2 A ) and Troester (79A) reviewed their properties and uses. Speight (77A) has summarized the uses of oxidized rubbers in anticorrosive and heat-resistant coatings. O n the subject of heat-resistant paints, Coe ( 4 A ) discussed the use of silicones. Stevens (78A) reviewed Lhe uses of polysulfides for coatings and sealants. Finally, Helms ( 9 A ) discussed zinc-filled inorganic coatings, which have definite anticorrosive properties.
INDUSTRfAL A N D ENGINEERING CHEMISTRY
Paints for Steel Attention continues to be devoted to the problem of getting the best and most economical coating for the specific end use. Tatton and Drew (76B) have prepared tables recommending the most suitable types of coatings for various uses. Since most of the paint used on steel is devoted to maintenance of existing structures, a suitable maintenance program (73B) is essential. Frye (7B) and Leahey ( 7 7B) also discussed proper maintenance programs, and Munger (74B) has outlined the requirements of an ideal maintenance coating. Zimmermann (77B) reported a study covering the interrelationship between surface preparation, film thickness, and paint composition. Blackledge (2B) also stressed the relationship between surface preparation and choice of paint, with particular emphasis on basic lead silicochromate. Hudson (9B) emphasized the protection of gas plant and equipment. The protection of steel immersed in fresh water is, in some respects, more difficult than protection against salt water. Shanks (75B) has described the methods and materials used by the U. S. Army Corps of Engineers, and Lewis and Kiewit (72%) covered the uses and tests for coatings for the Bureau of Reclamat ion. One recurring problem concerns the actual surface preparation and application techniques used on the job, which may not be those desired by the designer. Cody (5B) described the means used by the State of ft‘ashington to assure that inspectors are properly trained and that contractors know of and ure the approved techniques. A progress report was given by Bosch (3B) on an extensive investigation sponsored by the Paint Research Institute on minimum film thickness for steel protection. Exposures are not complete, but the inferiority of hand-brushing has been demonstrated. The importance of proper design in obtaining adequate protection with tank coatings was outlined by Aldrich (7B). I n this connection, an investigation by the Steel Structures Painting Council into the painting of welds. summarized by Keane and Bigos (7UB), has shown that the type of electrode used and the surface protection and clean-up around the weld are much more important than the type of primer in determin-
ing the life of the coating. Gohman (SB) described filiform corrosion, which is usually associated with smooth steel, and recommended methods of prevention. Efforts continue to develop a satisfactory method of predicting the performance of coatings in service, although actual service tests remain the final criterion. Bose and Mukerki (4B) compared accelerated weathering tests with actual exposure and found rather poor correlation, except between very similar Cormulations or when one specific property such as tint retention is investigated. Foster (6B) described some laboratory screening tests applicable to linings for chemical process equipment.
Application The preparation of the surface to be painted and the application of coatings remain the costly part of the use of paint, and more attention is being devoted to the development of more efficient and economical methods. Purchase (6C) has compared the various application methods and discussed the appropriate uses of each. Docherty and Hughes (3C) reviewed the various plastics used for corrosion prevention, with specific emphasis on application methods. The development of catalyzed coatings, such as epoxies, urethanes, and polyesters, has stimulated interest in the application problems associated with their use; Hutchinson (5C) described various types of equipment. I n the coating of smaller parts, fluidized bed coating has been very successful, since extremely thick coatings may be applied and resins which would otherwise not be practical because of insolubility may be used. Sherwood (7C) cited the advantages of this technique, and Borsch (7C) described its application to vinyl resins. I n other reports in this field, Casforth (2C) has investigated the hazards associated with sand-blasting and determined that sand-blasting will not ignite volatile solvents. Theis (8C) has described the internal cleaning and coating of plant pipelines in place. Hunter (4C) discussed modern techniques for preparation of masonry surfaces.
Miscellaneous Among other interesting developments are improvement in fire-retardant coatings. Johnson (70) described new developments in this field, especially the intumescent coatings. Hockridge (6D) discussed various methods of reducing the flammability of wood, particularly interior building boards, by impregnation and the use of suitable coatings. Gross ( 4 0 ) has studied factors influencing the results obtained by the radiant panel method of testing fire retardance; he demonstrated its value
in showing the performance of fire retardant coatings. New developments in the field of fungicides for paints were reviewed by Go11 and Snyder ( 3 0 ) . Whiteley (730) discussed the importance of fungicides in paints designed for tropical use and pointed out that most fungicides lose their effectiveness before the coating loses its integrity. The paint with good durability and satisfactory resistance to mold in tropical environments has not yet been developed. In other fields, Fitzgerald-Lee (20) and Stevens ( 1 2 0 ) have discussed the problems of finishing magnesium. Yenkin ( 1 4 0 ) has described a relatively new aluminum-asphalt roof coating, available in colors. Lumsden ( 9 0 ) has studied the preservation of poles and concluded that a mixture of pentachlorophenol and creosote is much more effective than either used alone. Durney (7D)has reported on a comparison of various industrial removers. Rules for the selection of colors in industrial plants were summarized by Kostalik (SO), and a n Australian report ( 1 1 0 ) suggested ways in which paint and color may be used to reduce industrial hazards. The new fluorescent pigments have a number of uses in maintenance finishes, as described by Hall ( 5 0 ) , and the National Safety Council (70D)has suggested ways in which these products may be used to promote salety.
Liferature Cited Newer Materials
(1A) Allan, L. H., Paint Manuj. 30, 161 (1960). (2A) Banks, R. E., Haszeldine, R. N., J . 011 &’ Colour Chemists’ Assoc. 42, 663 (1959). (311) Bardin, P. C., Znd. Finishing (Zndianapolzs 36, No. 12, 50 (1960). b,e, B. P., Chem. Eng. 67, No. 17, (4?&6 (1960). (5A) Elliott, A,, Dickson, J. H., Prod. Finishing (London) 13, No. 5, 54 (1960). (6A) Gray, V. R., J. Oil &’ Colour Chemists’ Assoc. 43, 10 (1960). (7A) Guffie, J., Can. Paint & Varnish Mag. 34, No. 7, 40, 79 (1960 (8A) Hampton, H. A., urd, R., Shearing, H. J., J. Oil &’ Colour Chemists’ Assoc. 43, 96 (1960). (9A) Helms, F. P., Corrosion 16, No. 6, 24 (1960). (10A) Howard, H. W., Radecke, F. T., Scheibli, P. R., Paint Technol., 24, No. 270, 22 (1960). (11A) Knaf, H. G., Znd. Finishing (Zndianapolis) 36, No. 6, 128 (1960). (12A) Kostiuk, E., Peintures, pigments, vernis 36,3 (1960). (13A) McGinnis, I. L., Forest Products J . 10, No. 2, 129 (1960). (14A) Modern Plastics 38, No. 4, 83, 182, 185 (1960). (15A) Patton, T. C., Paint Znd. Mag. 75, No.7, 18 (1960). (16A) Prods. Finishing (Cincinnati) 24, No. 7. 32 11960). (17A) Speight, C., Paint Manuf. 30, 323, 336 (1960). (18A) Stevens, W. H., J. Oil & Colour Chemists’ Assoc. 42, 663 (1959).
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(19A) Troester, F. W., Corrosion 16, No. 2, 14, 16, 18, 24 (1960). (20A) Wells, E. R., Paint Varnish Production 51, No. 3, 41 (1961). Maintenance (1B) Aldrich, C. K., Chem. Eng. 67, No. 16, 154 (1960). (2B) Blackledge. J. P.. Western Paint Rev. ‘ 46, No. 12, r2’(1960): (3B) Bosch, W., 0 8 6 . Dig. Federation SOC. Paint Technol. 32, 1602 (1960). (4B) Bose, S. K., Mukerki, S. N., Paznt Manuf. 30, No. 3, 88 (1960). (5B) Cody, L. W., O@c. Dig. Federation SOC.Paint Technol. 33, 199 (1961). (6B) Foster, R. S., Corrosion 16, No. 11, 26. 32 (1960). (7B)’,Fryd, S. C., OBc. Dig. Federation SOG. Paznt Technol. 32, 1642 (1960). (8B) Gohman, R. G., Ind. Anishine (In’ dianapolis) 35, No. 9;32 (1959). (9B) Hudson, J. C., Chem. @ Znd. (London) 1961. D. 3. (10B) Keane, J. D., Bigos, J., Corrosion 16,No.12,93 (1960). (11B) Leahey, M. .J., Master Painter Australia 12,No. 2, 17, 28 (1960). (12B) Lewis, P. W.. Kiewit, J. L., Corrosion 16; No. 6,‘9 (1960). (13B) Modern Sanitation 12, No. 4, 13, 50 11960). I (14B) Munger, C. G., Corrosion 16, No. 6, 22 (1960). (15B) Shanks, F. W., O ~ C Dig. . Federation SOC.Paint Technol. 32, 1627 (1960). Il6B) Tatton. W. H.. Drew. E. W.. ‘ Prhd. Finishing (London) 13, No. 12, 5 4
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(1?B) -Zimmermann, E. K., Paint Ind. Mag. 75, No. 10, 18 (1960). Application (1C) Borsch, R. J., Modern Plastics 37, No. 11, 124, 186 (1960). (2C) Casforth, N. D., Corrosion 16, No. 2, 20 (1960). (3C) Docherty, A. C., Hughes, H., Chem. t 3 Znd. (London) 1959,p. 1171. (4C) Hunter, Z., Wedtern Paint Rev. 46. No. 5, 34 (1960). (5C) Hutchinson, C. O., Forest Products J . 10. No. 9. 100. 441 (1960). (6C)’Purchase, ’ A. R . , Prod. Finishing (London) 13, No. 4, 81 (1960). (7C) Sherwood, P. W., Can. Paint C3 Varnish Mag. 34, No. 8, 22, 41 (1960). (8‘2) Theis, W. T., Corrosion 16. No. 6. 15, 26 (1960). Miscellaneous (1D) Durney, L. J., Prods. Finishing (Cincinnati) 24. No. 6. 39 (1960). (2D) Fitzge;ald:Lee, G., Prod. Finishing (London) 13, No. 9, 91 (1960). (3D) Goll, M., Snyder, H. D., Paint Znd. Mag. 75, No. 9, 24 (1960). (4D) Gross, D., Forest Pioducts J. 10. No. ‘ 1,’33 (1960). (5D) Hall, J. F., Jr., Paint Znd. Mag. 75, No. 6, 29 (1960). (6D) Hockridge, A. J., D~corator 59, No. 702, 57 (1960). (7D) Johnson, F. D., Paint 2nd. Mag. 75, No. 12, 12 (1960). (8D) Kostalik, J. F., lVe?tPm Paint Rev. 46, No. 3, 14, 16, 24 (1960). (9D) Lumsden, G. Q., Forest Products J . 10, No. 9, 456 (1960). (10D) Natl. Safety News 81, No. 4, 38 (1960). (11D) Paznt J . Australia New Zealand 4, No. 10, 30 (1960). (12D) Stevens, J. A., Prods. Finishing (Indianapolis) 24, No. 11, 74 (1960). (13D) Whiteley, P., J . 021 Colour Chemists’ Assoc. 43. 842 (1960). (14D) Yenkin, F., Am. Paint J. 45, No. 10, 32, 41 (1960). VOL. 53, NO.
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