Designation:B733−15StandardSpecificationforAutocatalytic(Electroless)Nickel-PhosphorusCoatingsonMetal1ThisstandardisissuedunderthefixeddesignationB733;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheU.S.DepartmentofDefense.1.Scope1.1Thisspecificationcoversrequirementsforautocatalytic(electroless)nickel-phosphoruscoatingsappliedfromaqueoussolutionstometallicproductsforengineering(functional)uses.1.2Thecoatingsarealloysofnickelandphosphoruspro-ducedbyautocatalyticchemicalreductionwithhypophosphite.Becausethedepositednickelalloyisacatalystforthereaction,theprocessisself-sustaining.Thechemicalandphysicalpropertiesofthedepositvaryprimarilywithitsphosphoruscontentandsubsequentheattreatment.Thechemicalmakeupoftheplatingsolutionandtheuseofthesolutioncanaffecttheporosityandcorrosionresistanceofthedeposit.Formoredetails,seeASTMSTP265(1)2andRefs(2)(3)(4)and(5).1.3Thecoatingsaregenerallydepositedfromacidicsolu-tionsoperatingatelevatedtemperatures.1.4Theprocessproducescoatingsofuniformthicknessonirregularlyshapedparts,providedtheplatingsolutioncircu-latesfreelyovertheirsurfaces.1.5Thecoatingshavemultifunctionalproperties,suchashardness,heathardenability,abrasion,wearandcorrosionresistance,magnetics,electricalconductivityprovidediffusionbarrier,andsolderability.Theyarealsousedforthesalvageofwornormismachinedparts.1.6Thelowphosphorus(2to4%P)coatingsaremicroc-rystallineandpossesshighas-platedhardness(620to750HK100).Thesecoatingsareusedinapplicationsrequiringabra-sionandwearresistance.1.7Lowerphosphorusdepositsintherangebetween1and3%phosphorusarealsomicrocrystalline.Thesecoatingsareusedinelectronicapplicationsprovidingsolderability,bondability,increasedelectricalconductivity,andresistancetostrongalkalisolutions.1.8Themediumpho...
