ASTM_B_253_-_11_2017.pdf

Designation:B25311(Reapproved 2017)Standard Guide forPreparation of Aluminum Alloys for Electroplating1This standard is issued under the fixed designation B253;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This guide covers cleaning and conditioning treatmentsused before metal deposition(Section 5),and immersiondeposit/strike procedures(Section 6)that enhance the adhesionof metals that are subsequently applied to aluminum productsby electrodeposition or by autocatalytic chemical reduction.1.2 The following immersion deposit/strike procedures arecovered: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 glyco-late strike(6.5).1.2.4 Zinc immersion with acid or alkaline electrolessnickel strike.1.2.5 Tin immersion with bronze strike(6.6).1.3 From the processing point of view,these procedures areexpected to give deposits on aluminum alloys that are approxi-mately equivalent with respect to adherence.Corrosion perfor-mance is affected by many factors,however,including theprocedure used to prepare the aluminum alloy for electroplat-ing.1.4 This guide is intended to aid electroplaters in preparingaluminum and its alloys for electroplating.1.5 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.For specificprecautionary statements see Section 7 and Appendix X1.1.7 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2B85 Specification for Aluminum-Alloy Die CastingsB179 Specification for Aluminum Alloys in Ingot and Mol-ten Forms for Castings from All Casting ProcessesB209 Specification for Aluminum and Aluminum-AlloySheet and PlateB209M Specification for Aluminum and Aluminum-AlloySheet and Plate(Metric)B221 Specification for Aluminum and Aluminum-Alloy Ex-truded Bars,Rods,Wire,Profiles,and TubesB221M Specification for Aluminum and Aluminum-AlloyExtruded Bars,Rods,Wire,Profiles,and Tubes(Metric)B322 Guide for Cleaning Metals Prior to ElectroplatingB432 Specification for Copper and Copper Alloy Clad SteelPlateE527 Practice for Numbering Metals and Alloys in theUnified Numbering System(UNS)3.Significance and Use3.1 Various metals are deposited on aluminum alloys toobtain a decorative or engineering finish.The electroplatesapplied 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 decreasecontact resistance or to improve surface conductivity;brass,copper,nickel,or tin for assembly by soft soldering;chromiumto reduce friction and obtain increased resistance to wear;zincfor threaded parts where organic lubricants are not permissible;tin or lead is frequently employed to reduce friction on bearingsurfaces.Nickel plus chromium or copper plus nickel pluschromium is used in decorative applications.Nickel plus brassplus lacquer or copper plus nickel plus brass plus lacquer is1This guide is under the jurisdiction of ASTM Committee B08 on Metallic andInorganic Coatings and is the direct responsibility of Subcommittee B08.02 on PreTreatment.Current edition approved May 1,2017.Published May 2017.Originallyapproved in 1951.Last previous edition approved in 2011 as B253 11.DOI:10.1520/B0253-11R7.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 also used for decorative finishes,sometimes with the brassoxidized and relieved in various ways.3.1.1 Ele