ASTM A90/A90M-21

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.

3.2?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?UnitsThe 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.

1.4?This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.5?This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.