water, and alcohol, and allowed to dry in a near vertical position. After the specimens are dry the color difference between the tested and untested portions of the specimens is determined and is used as a measure of the specimens' weather resistance. These values are plotted as a function of the color-retention values after three years' exposure in figure 5. The correlation is improved over that obtained for the boiling acid solubility as indicated by the smaller residual standard deviations (see table 7) for the fits of the least squares lines. Although the correlation between the color retention and the results of the boiling cupric chloride test is better than that with the boiling acid solubility test, it is felt that longer exposure times are necessary before any recommendations for specification changes are made. This increased exposure time is necessary because the color retention after three years' exposure of the enamels that passed the boiling acid solubility test is adequate (more than 94) at all sites except Kure Beach. 3.8. Correlation with Enamels in a Previous Exposure Test Kure Beach, Washington, and Los Angeles are three sites common to both the current test and a test initiated in 1956 [11]. The average color-retention data for the enamels exposed at these sites in both tests are included in table 8. These data indicate that the enamels in the current test are as durable as the early porcelain enamels on aluminum at all sites, and at the milder sites, Washington and Los Angeles, are as good as the acid resistant enamels on steel. Since it was 3.9. Nature-Tone Enamels on Aluminum Seven nature-tone or mat enamels on aluminum were added to the test program after the one-year inspection. The initial gloss, color, and thickness of these enamels are presented in table 9 while the colorretention and percentage gloss-retained data for these enamels are presented in table 10. These data indicate good gloss and color retention for most enamels at all sites. One enamel, AM-7, spalled enough to constitute failure at all sites. TABLE 9. Initial data for nature-tone enamels on aluminum Enamel AM-2 Lt. brown. AAAAABÁ The 45-deg specular gloss was measured in accordance with ASTM designation C-346. b The thickness was measured in accordance with ASTM designation E-376. The boiling acid solubility was determined in accordance with ASTM designation C-283. d The acid spot test ratings were determined in accordance with ASTM designation C-282. TABLE 10. Gloss and color retention of nature-tone enamels on aluminum after two years' exposure [1] Rushmer, M. A., and Burdick, M. D., Weather Resistance of Porcelain Enamels: Effect of Exposure Site and Other Variables after Seven Years, Nat. Bur. Stand. (U.S.), Bldg. Sci. Ser. 4, 16 pages (May 1966). [2] Resistance of Porcelain Enameled Utensils to Boiling Acid, C-283 ASTM Book of Standards, Pt. 13, (1968). [3] Acid Resistance of Porcelain Enamels (Citric Acid Spot Test), C-282 ASTM Book of Standards, Pt. 13, (1968). [4] Recommended Practice for Measurement of Coating Thickness by Magnetic Field or Eddy Current (Electromagnetic) Test Methods, E-376 ASTM Book of Standards, Pt. 3, (1968). [5] Gloss of Ceramic Materials, 45-Deg. Specular, C-346, ASTM Book of Standards, Pt. 13, (1968). [6] Instrumental Evaluation of Color Differences of Opaque Materials, D-2244, ASTM Book of Standards, Pt. 21, (1968). [7] Potter, A., Using an electronic computer to reduce weathering data, Proceedings of the Porcelain Enamel Institute Forum 20, 73 (1958). [8] Test for Spalling Resistance of Porcelain Enameled Aluminum, C-486, ASTM Book of Standards, Pt. 13, (1968). [9] Natrella, M. G., Some tests which are independent of the form of distribution, Chapter 16, Experimental Statistics, Nat. Bur. Stand. (U.S.), Handb. 91 (August 1963). [10] Recommended Specification for Architectural Porcelain Enamel on Aluminum for Exterior Use, PEI: ALS-105, Porcelain Enamel Institute, (1969). [11] Moore, D. G., and Potter, A., Effect of Exposure Site on Weather Resistance of Porcelain Enamels Exposed for Three Years, Nat. Bur. Stand. (U.S.), Monogr. 44, 13 pages (April 1962). U. S. GOVERNMENT PRINTING OFFICE: 1970 392-251/156 NATIONAL BUREAU OF STANDARDS The National Bureau of Standards was established by an act of Congress March 3, 1901. Today, in addition to serving as the Nation's central measurement laboratory, the Bureau is a principal focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. To this end the Bureau conducts research and provides central national services in four broad program areas. These are: (1) basic measurements and standards, (2) materials measurements and standards, (3) technological measurements and standards, and (4) transfer of technology. The Bureau comprises the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Center for Radiation Research, the Center for Computer Sciences and Technology, and the Office for Information Programs. THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of an Office of Measurement Services and the following technical divisions: Applied Mathematics-Electricity-Metrology-Mechanics-Heat-Atomic and Molecular Physics-Radio Physics -Radio Engineering -Time and Frequency-Astrophysics-Cryogenics." THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to improved methods of measurement standards, and data on the properties of well-characterized materials needed by industry, commerce, educational institutions, and Government; develops, produces, and distributes standard reference materials; relates the physical and chemical properties of materials to their behavior and their interaction with their environments; and provides advisory and research services to other Government agencies. The Institute consists of an Office of Standard Reference Materials and the following divisions: Analytical Chemistry-Polymers-Metallurgy-Inorganic Materials-Physical Chemistry. THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to promote the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations in the development of technological standards, and test methodologies; and provides advisory and research services for Federal, state, and local government agencies. The Institute consists of the following technical divisions and offices: Engineering Standards-Weights and Measures - Invention and Innovation - Vehicle Systems Research-Product Evaluation-Building Research-Instrument Shops-Measurement Engineering-Electronic Technology-Technical Analysis. THE CENTER FOR RADIATION RESEARCH engages in research, measurement, and application of radiation to the solution of Bureau mission problems and the problems of other agencies and institutions. The Center consists of the following divisions: Reactor Radiation-Linac Radiation-Nuclear Radiation-Applied Radiation. 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THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS and other agencies of the Federal government; promotes the development of the National Standard Reference Data System and a system of information analysis centers dealing with the broader aspects of the National Measurement System, and provides appropriate services to ensure that the NBS staff has optimum accessibility to the scientific information of the world. The Office consists of the following organizational units: Office of Standard Reference Data-Clearinghouse for Federal Scientific and Technical 1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234. Located at Boulder, Colorado 80302. Located at 5285 Port Royal Road, Springfield, Virginia 22151. |