Home>ASTM Standards>ASTM B816-00(R2021) pdf free download

ASTM B816-00(R2021) pdf free download

ASTM B816-00(R2021) pdf free download.Standard Specification for Coatings of Cadmium-Zinc Mechanically Deposited
7.3.1 General—The coating on all readily visible surfaces shall be uniform in appearance, well compacted, and complete in coverage. Superficial staining from rinsing and drying and mild variations in color and luster are acceptable.
7.3.2 Surface Defects—Defects and variations in appear- ance in the coating that arise from surface conditions of the substrate (scratches, pores, roll marks, inclusions, etc.) and that persist in the coating despite the observance of good metal finishing practices shall not be cause for rejection. N OTE 1—Coatings generally perform better in service when the substrate over which they are applied is smooth and free of torn metal, inclusions, pores, and other defects. The specifications covering the unfinished products should provide limits for these defects. A metal finisher can often remove defects through special treatments, such as grinding, polishing, abrasive blasting, chemical etches, and electropolish- ing. However, these are not normal in the treatment steps preceding the application of the coating. When they are desired, they are the subject of special agreement between the purchaser and the seller.
7.4.2 Significant Surfaces—Significant surfaces are usually defined as those normally visible (directly or by reflection) that are essential to the appearance and serviceability of the article when assembled in normal position; or that can be the source of corrosion products that deface visible surfaces on the assembled article. Significant surfaces are further defined at those surfaces that are identified as such by the purchaser, for example, by indicating them on an engineering drawing of the product or by marking a sample item of product.
7.4.3 Minimum Thickness Requirement—The coating re- quirement of this specification is a minimum requirement; that is, the coating thickness is required to equal or exceed the specified thickness everywhere on the significant surfaces. Variation in the thickness from point to point on an article and from article to article in a production lot is inherent in mechanically deposited coatings. Therefore, if all of the articles in a production lot are to meet the thickness requirement, the average coating thickness for the production lot as a whole will be greater than the specified minimum. N OTE 2—The thickness of mechanically deposited coatings varies from point to point on the surface of a product, characteristically tending to be thicker on flat surfaces, and thinner at exposed edges, sharp projections, shielded or recessed areas, and interior corners and holes, depending on the dimensions, with such thinner areas often being exempted from thickness requirements. N OTE 3—Processes used to produce Type II finishes remove some ofthe coating. Because thickness requirements apply to the finished article, additional thicknesses may have to be applied to compensate for the metal removed in the Type II process.
The organic coating or lubricant shall be removed from Type IId coatings before the salt spray test or the test can be run on articles that are withdrawn from processing before the organic coating is applied. N OTE 4—In many instances, there is no direct relation between the results of an accelerated corrosion test and the resistance to corrosion in other tests or actual environments, because several factors that influence the progress of corrosion, such as the formation of protective film, vary greatly with the conditions encountered. The results obtained in the test should not, therefore, be regarded as a direct guide to the corrosion resistance ofthe tested materials in all environments where these materials may be used. Also, performance of different materials in the test cannot always be taken as a direct guide to the relative corrosion resistance of these materials in service.

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