Active Standard ASTM B253 | Developed by Subcommittee: B08.02
Book of Standards Volume: 02.05
Historical (view previous versions of standard)
Significance and Use
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.
Electroless nickel may be applied as a barrier layer prior to other deposits, or for engineering purposes.
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 and health practices and determine the applicability of regulatory limitations prior to use. For specific precautionary statements see Section 7 and Appendix X1.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
B85 Specification for Aluminum-Alloy Die Castings
B179 Specification for Aluminum Alloys in Ingot and Molten Forms for Castings from All Casting Processes
B209 Specification for Aluminum and Aluminum-Alloy Sheet and Plate
B209M Specification for Aluminum and Aluminum-Alloy Sheet and Plate (Metric)
B221 Specification for Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes
B221M Specification for Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes (Metric)
B322 Guide for Cleaning Metals Prior to Electroplating
B432 Specification for Copper and Copper Alloy Clad Steel Plate
E527 Practice for Numbering Metals and Alloys in the Unified Numbering System (UNS)
ICS Number Code 25.220.10 (Surface preparation)