ASTM A90 – Standard Test Method for Weight [Mass] of Coating on Iron and Steel Articles with Zinc or Zinc-Alloy Coatings
Significance and Use
3.1 This test method provides a standard method for determining the weight [mass] of zinc coatings on iron or steel products, and for evaluating conformance of such products to a material specification under the jurisdiction of ASTM Committee A05 and its subcommittees as designated by a purchaser in a purchase order or contract.
3.1.1 This test method may be and is used by other ASTM Committees and other standards writing bodies for the purpose of conformance testing.
3.1.2 The material condition at the time of testing, sampling frequency, specimen location and orientation, reporting requirements, and other test parameters are contained in the pertinent material specification or in a general requirement specification for the particular product form.
3.1.3 A coating of zinc on iron or steel articles provides protection against corrosion. As the protection is provided by sacrificial loss of zinc, the degree of protection is proportional to the weight [mass] of zinc coating. Specifications for zinc-coated articles frequently provide for different designations or classes of coating so that the purchaser can select the coating weight [mass] most suitable for the intended application.
3.2 This test method determines the average coating weight [mass] over a specified area, from which the average thickness can be calculated. Other test methods not described herein can determine the thickness directly at point locations on the coating; in such cases, the required test method is described in that material specification or by reference to another appropriate test method standard.
1.1 This test method covers procedures for determining the weight [mass] of coating on iron or steel sheet, wire, and other articles in which the coating is zinc or a zinc alloy, such as zinc-5 % aluminum (including zinc-5 % aluminum-mischmetal and zinc-5 % aluminum-0.1 % magnesium), zinc-aluminum-magnesium (including zinc-5 to 9 % aluminum-magnesium and zinc-9 to 13 % aluminum-magnesium) or 55 % aluminum-zinc. In the body of this test method, reference to zinc coating shall be interpreted to also include zinc alloy coating except where specifically stated otherwise.
1.2 Units—The final results determined by this test method shall be expressed in inch-pound units or SI units, depending on the units used in the material specification to which the results are to be compared. Certain portions of the procedure involving determination of specimen weight [mass] have traditionally been performed in SI units, and corresponding inch-pound units are not included.
1.3 For sheet products, the final results are expressed as either coating weight [mass] total both sides, or coating weight [mass] separately on each side, depending on the specified requirements.