Mechanical assisted electroless barrel-plating Ni-P coatings on magnesium alloy

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1、ActaMetall.Sin.(Engl.Lett.)Vol.22No.3pp225-232June2009Mechanicalassistedelectrolessbarrel-platingNi-PcoatingsonmagnesiumalloyZhaoxiaPING,JuntaoYUAN,YedongHE¤andXiaogangLIBeijingKeyLaboratoryforCorrosion,ErosionandSurfaceTechnology,UniversityofScienceandTechnol-ogyBeijing,Beijing100083,ChinaMa

2、nuscriptreceived15July2008;inrevisedform24October2008Amechanicallyassistedelectrolessbarrel-platingNi-PwascarriedoutinarollingdrumcontainingMgalloyspecimensandceramicballs,whichwassubmergedinabathcontainingelectrolessplatingsolution.ItisdemonstratedthattheNi-Pcoatingsdepositedbythisnoveltechn

3、iquehaveacrystallizedNi-Psolidsolutionstructure,showing¯ne-grains,higherhardness,andhighercorrosionresistancecomparedwiththeconventionalelectrolessplatedamorphousNi-Pcoatings.Afterheattreatment±at400Cfor1h,thestructureofsuchNi-PcoatingsweretransformedtoastructurewithNi-Ni3Pdoublephases,andcra

4、cksinthesecoatingscouldnotbeobserved,whereascracksappearedseriouslyintheconventionalelectrolessplatedNi-Pcoatingaftersameheattreatment.Therefore,bothhardnessandcorrosionresistanceoftheseNi-Pcoatingscanbeimprovedfurtherbyheattreatment.Allofthesebene¯ciale®ectscanbeattributedtotheroleofmechanic

5、alattritionduringthemechanicallyassistedelectrolessbarrel-platingprocess.KEYWORDSMechanicallyassistedelectrolessbarrel-plating;Ni-Pcoating;Crystallization;Corrosionresistance;Microhardness1IntroductionMechanicallyassistedplatinghasbeeninvestigatedbymanyresearchers[1¡9].Theearlystudyfocusesont

6、hechangeinthedepletionzoneatthedepositsurfacebyamechani-calmeans[1¡5].Intheoldendays,thehighspeedplatingprocesswasexploredinthe1970s[1¡5].Thehardparticleswithhighporosityweremovingandcontractingwiththecathodesurface.Thehighporosityofhardparticlescanallowreadyaccessofelectrolytetotheelectrodes

7、urface.Thethicknessofthedepletionlayerdecreased,andthelimitingplatingspeedincreased.However,therecentstudyconcentratesonin-situmechanicaltreatmentsofcoatings[6¡9].Thestudyresultsshowthatthemechanicalattritionassistantelectroplatedandelectrole