ASTM B253-11(2022)

SIGNIFICANCE AND USE 3.1 Various metals are deposited on aluminum alloys to obtain a decorative or engineering finish. The electroplates applied are usually chromium, nickel, copper, brass, silver, tin, lead, cadmium, zinc, gold, and combinations of these. Silver, tin, or gold is applied to electrical equipment to decrease contact resistance or to improve surface conductivity; brass, copper, nickel, or tin for assembly by soft soldering; chromium to reduce friction and obtain increased resistance to wear; zinc for threaded parts where organic lubricants are not permissible; tin or lead is frequently employed to reduce friction on bearing surfaces. Nickel plus chromium or copper plus nickel plus chromium is used in decorative applications. Nickel plus brass plus lacquer or copper plus nickel plus brass plus lacquer is also used for decorative finishes, sometimes with the brass oxidized and relieved in various ways. 3.1.1 Electroless nickel may be applied as a barrier layer prior to other deposits, or for engineering purposes. 3.2 The preparation of aluminum and aluminum alloy mandrels for electroforming is described in Practice B432. SCOPE 1.1 This guide covers cleaning and conditioning treatments used before metal deposition (Section 5), and immersion deposit/strike procedures (Section 6) that enhance the adhesion of metals that are subsequently applied to aluminum products by electrodeposition or by autocatalytic chemical reduction. 1.2 The following immersion deposit/strike procedures are covered: 1.2.1 Zinc immersion with optional copper strike (6.3). 1.2.2 Zinc immersion with neutral nickel strike (6.4). 1.2.3 Zinc immersion with acetate-buffered, nickel glycolate strike (6.5). 1.2.4 Zinc immersion with acid or alkaline electroless nickel strike. 1.2.5 Tin immersion with bronze strike (6.6). 1.3 From the processing point of view, these procedures are expected to give deposits on aluminum alloys that are approximately equivalent with respect to adherence. Corrosion performance is affected by many factors, however, including the procedure used to prepare the aluminum alloy for electroplating. 1.4 This guide is intended to aid electroplaters in preparing aluminum and its alloys for electroplating. 1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.6 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. For specific precautionary statements see Section 7 and Appendix X1. 1.7 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.