ASTM_B_319_-_91_2014.pdf

Designation:B31991(Reapproved 2014)Endorsed by AmericanElectroplaters SocietyEndorsed by NationalAssociation of Metal FinishersStandard Guide forPreparation of Lead and Lead Alloys for Electroplating1This standard is issued under the fixed designation B319;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.1.Scope1.1 This guide provides methods for preparing lead or leadalloy products for the application of electroplated or autocata-lytic coatings.1.2 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.2.Referenced Documents2.1 ASTM Standards:2B281 Practice for Preparation of Copper and Copper-BaseAlloys for Electroplating and Conversion Coatings3.Significance and Use3.1 The preparation of lead and lead-alloy surfaces forelectroplating is often critical to the successful performance ofelectrodeposited and autocatalytic metallic coatings.3.2 This standard outlines the process operation proceduresand processing solutions required,that lead to satisfactoryelectrodeposited metallic coatings(including undercoating)onsurfaces of lead and lead-alloys.4.Nature of Lead4.1 The tensile strength of lead and lead alloys ranges from15 to 35 MPa(2000 to 5000 psi),therefore,the measuredadhesion of electroplated coatings cannot be greater than thesevalues.4.2 Difficulties in applying high-quality electroplated coat-ings to lead are due to the following properties of lead:4.2.1 The very active chemical nature of lead,leading to theformation of oxide films in air,4.2.2 The fact that the lead surface will form films ofinsoluble lead salts with most acids used in pickling,4.2.3 The ease with which lead diffuses in contact withnonferrous metals,and4.2.4 The poor resistance to plastic deformation duringpolishing.5.Process Precautions5.1 The following process precautions should be observed:5.1.1 Precleaning of raw castings is sometimes necessary toremove mold parting compounds,surface oxides,and residuesfrom recessed areas which are never reached by polishing-wheel or scratch-brush operations(Section 6).5.1.2 In high-speed type cyanide electroplating solutions,the initial current density must be controlled and kept lowenough so that no gassing occurs to cause poor adhesion.Thisis revealed as groups of blisters in the high-current-densityareas of the electroplate.5.1.3 If a strike electroplate is used,it should be thickenough to prevent the next electroplating solution from attack-ing the basis lead.Acopper or nickel strike 2.5 m thick shouldbe used,but because there are so many variables involved,nospecific recommendations can be made.5.1.4 Preplates should be of such thickness that completealloying with the lead does not take place,an occurrence thatcauses poor adhesion of subsequent deposits.This defect isindicated by blistering after prolonged storage or after anaccelerated aging test.5.1.5 The lead compounds formed by the action of acids andalkalies most often used in electroplating are not water soluble.Caution must be taken to remove or prevent the formation ofthese to eliminate subsequent adhesion failure.Acids thatcannot be used are sulfuric,hydrochloric,and hydrofluoric.(Acids that can be used are sulfamic and fluoboric.)Alkaliesshould not be high in caustic content.Mild or buffered cleanersare preferred in order to minimize attack on the basis leadsurface.5.1.6 Engraving of electroplated finishes on lead cannot beperformed on deposits over 5 m thick as the deposit will tear1This 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 Nov.1,2014.Published November 2014.Originallyapproved in 1957.Last previous edition approved in 2009 as B319 91(2009).DOI:10.1520/B0319-91R14.2For 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 States1 away from the lead at cross cuts.Engine turning by burnishingcan be done on any thickness of deposits.5.1.7 Polishing and coloring of the deposit must be per-formed at slow speeds,and with loose or cooled buffs toeliminate overheating and flowing of basis metal.6.Precleaning6.1 Remove fins and parting lines by use of trimming dies orby scraping,filing,or grinding.Some machining may be doneat this point,such as drilling holes,or m