This specification covers single- and double-reduced tin mill black plate electrolytically coated with chromium and chromium oxide. The steel shall be furnished in coils and cut lengths for use in manufacture of cans, closures, crowns, and other products. The weights of the total coating which is made up of chromium metal and chromium oxides shall be determined. Single-reduced base steels shall be produced with ground roll finishes (type 7B-A for smooth finish containing fine grit lines and type 7C-A for smooth finish with grit lines), and shot-blasted and/or textured roll finishes (type 5C-A for shot-blasted finish for general applications and type 5D-A for special applications). Double-reduced base steels shall be produced only with ground roll finishes of type 7C-A. The steels shall be furnished with extremely thin oil film on both surfaces.

1.1 This specification covers single- and double-reduced tin mill black plate electrolytically coated with chromium and chromium oxide. The steel is furnished in coils and cut lengths for use in the manufacture of cans, closures, crowns, and other products.

1.2 This specification is applicable to orders in either inch-pound units (as A657) which is supplied in thicknesses from 0.0050 to 0.0149 in. or in SI units [as A657M] which is supplied in thicknesses from 0.127 to 0.378 mm.

1.3 The values stated in either inch-pound or SI units are to be regarded as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents. Therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with this specification.

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.