汽车设计与维修人员培训课件磷化喷漆

Zincphosphating&lacquering2ContentIntroduction:►Zn-phosphatingspecifictoAluminium►Exampleofpaintingprocess3Zn-phosphatingspecifictoAluminium4Zinc-phosphatingofaluminiumIntroduction:►Thezinc-phosphatingtreatmentisusedtoclean,etchandappliedaprotectiveandcoat-preservinglayer,afterhavingbondthemainpartsofthecarbody.►Rightafterthezinc-phosphating,inthesameline,thecarbodiesareelectropainted.►Thisstepisapplieddirectlyinthedifferentcarcompany,withdifferentinstallationsanddifferentconditions.►Partsinaluminiumandpartsingalvanisedsteelsaretreatedtogether,theratiobetweenthetwomaterialcanbeverydifferent.►Thisisjustashortintroductiontothistopic,usuallypre-treatmentandZn-phosphatingchemicalssupplierslikeChemetalorHenkelprovideagoodsupportinthisdomain.5Zinc-phosphatingofaluminiumDifferentstepsintheZinc-phosphating1.Mildalkalinecleaning2.ActivationwithaTi-phosphatecolloidalsolution→lightformationofaphosphatelayer3.Zinc-phosphating:►Phosphate►Formationofametalcationlayer:Zn-Ni-Mn►Fluoride:ThiselementisimportantregardingthebuildingofthelayerontheAlandSteel►Accelerator:Sodiumnitrite(NaNO2)orHydrogenperoxide(H2O2)andHydroxylamine(NH2OH)4.Passivation►Before:CrVI,CrIII►Moreenvironmentalfriendlyalternativeusedtoday:ZirconiumFluoride►InsomeOEM,onlyarinsingwithwaterisused6ImmersionphosphatingofSteel,ZincandAluminium:SteelZincAluminiumZinc-phosphatingofaluminiumTheideallayerstructureregardingthecorrosionprotectionis:•manycompactandorderedmicrocristalsofthesamesize•homogenouscoverageofthesurface•epitaxialorientationofthecristals7ReactionsinvolvedintheZinc-phosphatingprocessonAluminium►OxideetchingAl2O3+6H+2Al3++3H2OComplexformation:Al3++6F-AlF6-AlOOH+6HFAlF6---+3H++2H2O►Based-metalattackAl+3H+Al3++1½H2(Gas)►ComplexFormationofAl3+withSodiumundFluorideAl3++6F-+3Na+Na3AlF6(cryolite-sludge)►Buildinglayeronthemetal2Mn+++Zn+++2H2PO4-+4H2OMn2Zn(O4)2·4H2ZnMn-Phosphate3Zn+++2H2PO4-+4H2OZn3(PO4)2·4H2O+4H+Zinc-phosphatingofaluminium8Fluorideadditionisimperative►withoutanyFluoride,thealuminiumphosphatingresultsonlyinapartialcoverage►butattoohighcontent,theetchingprocessleadstoablacklayer(passivation)TypicalFluoridecontent:►Usingsprayinsallation:Freefluoride:150-170mg/l►Byimmersionbath:Freefluoride:260mg/l(SiF6)Thezinc-phosphatingbuildingonsteelisdisturbedbythealuminiumcontentinthebath,becauseitactasapoison:►With1mg/lAl3+,lightdegenerationofthezinc-phosphatingcristal,leaksinthesurfacecoverage►With5mg/lAl3+,nosurfacelayercanbebuildonthesteelsurface→Al3+havetobepushedawayfromthesurface,whichcanbeachievedbythecryoliteformationZinc-phosphatingofaluminium9Zinc-phosphatinglayerapplicationByanimmersionprocess:withhighturbulenceinthebathInpraticalwith30-40%AluminiumcarbodyBysprayinstallation:Inpraticalwith75%AluminiumcarbodyAnozzlesarrangementatthebottomofthebathareheretoproduceaflowrateofatleast0.4m/swhilstensuringthatthemaximumimpactdoesnotexceed1m/sFlowrateoverthecarbody(m/s)Zinc-phosphatingofaluminium10►AluminiumphosphatingwithdifferentfluoridecontentsZinc-phosphatingofaluminium11Cryolite(Na3AlF6)precipitation:►Formationofcryoliteisnecessary,toremovethedissolvedaluminium(whichactsasapoison)fromthephosphatingbath.►Theprecipitionofcryolite,hardtocontolforallimmersionbath,mustbewellsupervisedNaFDefectofaKTLlayerthroughcryoliteZinc-phosphatingofaluminium12Themainparametersinvolvedinthecyolite(Na3AlF6)precipitationare:►Sodiumconcentration►Fluorconcentration►FlowratePrecipitationofcryoliteasafunctionofNaandFWithaspraysystem,thecryoliteprecipitationisnotsoimportant,asthecarbodiesarenotdeepinginabathFreeFluor[ppm]Sodium[g/l]Zinc-phosphatingofaluminium13Themainparametersinvolvedinthecryolite(Na3AlF6)precipitationare:►Sodiumconcentration►Fluorconcentration►FlowratePhophatecoverageversuspercentageofcryoliteF(free)200ppmWarning:Thecryoliteprecipitationispromotingbyhighsodiumconcentration,buthighsodiumconcentrationpreventtheformationofaphosphatelayer!Zinc-phosphatingofaluminiumCryoliteZn-phosphatecoverage14Cryolite(Na3AlF6)precipitation:►Cryolitehavetoberemovedbyafilterpressordirectfiltration►Cryoliteslurriesareveryhardandformedacrustonthephosphatingline,whichisveryhardtoremoved.►AcidcleaninghastobedoneregularlySlurry:about10g/m2totreatfromthealuminiumsurfaceZinc-phosphatingofaluminium15►Flowrateinthebathmustbecontrolledforagoodqualitylayer►Al3+inthebath:toohighconcentrationdisturbsZn-phosphatinglayeronsteelNeedtoremoveAl3+byprecipitatingcryolite(Na3AlF6)NeedtoaddNaandFbutincontrolledquantities►AddNaandFinbalancedratioforcryoliteprecipitation(unbalanced=Al3+remainsinsolution)►ControlNa:toohighlevelpreventZn-phosphatelayer►ControleF:toolowlevel=partialcoverageofZn-phosphatelayer►Needtoremoveprecipitatedcryoliteotherwisecreatessurfacesdefects=filtrationsysteminbathsSummary:Zinc-phosphatingofaluminium16Exampleofpaintingprocess17Carbodiespretreatment:12immersionbathsEveryhiddenrecessescanbereachedandemptyeasilywiththeRodipprocessRoDipprocess:Pretreatmentandlacqueringcarbodies18Ineveybath,thecarbodyturnarounditsownaxisintheverticaldirectionRoDipprocess:Pret