A Dream Come True for Fastener Coaters and Users?

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Sibyl Harris
6 years ago
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1 ArmorGalv Zinc/IronAlloyThermalDiffusionCoating ADreamComeTrueforFastenerCoatersandUsers? Traditionally,fastenerswerecoatedtoprovidethemwithcorrosionresistanceand propertorquetension(coefficientoffriction)characteristics,whiletryingtoavoid inducingthemwiththecatastrophicaffectsofhydrogenembrittlement.today, thereistheaddedrequirement,andchallenge,thattheprocessofcoatingthe fastenersbeenvironmentallyfriendly,andthattheresultingcoatingitselfbenontoxicandchromefree. COATINGCONUNDRUMS: THEPROBLEM Howdoyoucoattheentirefastenerwhilenotundercoatingtherecessesor fillingthemwithexcessivematerial? Howdoyoueasilycoattheinternalthreadsofnutsuniformly? Howdoyoucoatlongfastenersuniformly? Howdoyoucoattowhateverthicknessisneeded 10micronsor100 microns? HowdoyoueliminateHydrogenEmbrittlement? ISTHEENTIREFASTENERREALLYIMPORTANT? Thereareafewdifferentmethodsfortestingthecorrosionresistanceoffastener coatingsdependingupontheirfunctionandenduse.thesevariousmethods accountfordifferentcorrosiveenvironmentsandconditionstowhichthecoated fastenerwillbesubjected,sotheyare,bydefinition,quitedifferentfromeachother viz.,saltspray,kesternich,etc.thereare,however,twoimportantelementsthatall ofthesemethodshaveincommon. Thefirst,ofcourse,isthatfailureoccurswhenbasemetalcorrosionappears. Thesecondisthatonly significant surfacesaresubjecttoevaluation.surfaces thatareconsiderednottobe significant include: Sharpedges Rootsofthread Headrecesses Thesesurfacesdonotcoatwellbyelectro plating,mechanicalplating,anddip/spin methods,sothereisnosenseevaluatingthemwhentheycannotreallybeprotected inthefirstplace.but,ultimately,thesesurfacesarepartofthefastener,andare,in fact,quitesignificanttothelong termsurvivalandfunctioningofthefastener.

2 THESOLUTION ArmorGalv THERMALDIFFUSION(HUH?) AnEnglishmetallurgistnamedSherardCowper ColesinventedThermalDiffusion in1904.hediscoveredthatbyheatingaspecialblendofdryzincdustwithsteel partsinaclosedcylindertoatemperatureofatleast650degreesfresultedina uniformcorrosionresistantzinc/ironalloycoating. ThisprocesshasbeenusedinEnglandeversincethenunderthenameof Sherardizing,whichhasbeenappliedbyBodycote,Int l.recently,advanceshave beenmadeinthistechnologytoimproveitsefficiencyandreproducibility,anditis nowavailableintheunitedstatesunderthetradenameofarmorgalv. Belowisapictureoffastenerswithacaptivewasherthatwerecoatedwith ArmorGalv bychem PlateIndustries,inElkGroveVillage,IL. NoticethattheArmorGalv coatingisextremelyuniform,obviatingtheneedto designateportionsofafasteneras insignificant.thewholefastenerissignificant andcoated!saltsprayresultsofgreaterthan1,000hoursarecommon. CANArmorGalv REPLACECADMIUM? Eversince1971whentheJapanesecourtfoundtheMitsuiMiningandSmelting Companyguiltyofcausingasevereoutbreakof ItaiItai disease,betterknownas cadmiumpoisoning,cadmiumhasbeenvirtuallybannedtheworldover. Themainbenefitsofcadmiumwereitsanti gallingproperties,anditsabilitytonot seize inthepresenceofitsowncorrosionproductsduetoitsinherentlubricity properties. Astainlesssteelscrew,whencadmiumplated,couldeasilybedrivenwithout galling.

Acadmium platedboltcouldusuallybeunscrewedafteryearsofservice,whereas zincplatedboltstotallyseizeupandhavetobecutortorchedforremoval.

3 Acadmium platedboltcouldusuallybeunscrewedafteryearsofservice,whereas zincplatedboltstotallyseizeupandhavetobecutortorchedforremoval. StainlesssteelfastenerscoatedwithArmorGalv exhibitthesameabilitytodriveas docadmiumplatedones,andarmorgalv nut/boltassembliesareeasilyunscrewed evenafterbeingsubjectedto1,000hoursofsaltspray. WILLArmorGalv INDUCEHYDROGENEMBRITTLEMENTTOHEATTREATED FASTENERS? Absolutelynot!Fastenersarecoatedusingtemperaturesof,atleast,650degreesF forover90minutesinacompletelydryenvironment.atthistimeandtemperature matrix,thereisnochanceofinducinghydrogenembrittlement,andwouldeven relieveanyresidualstressesthatmightalreadybepresentinthefastenerdueto otherfactors.thisisverifiedinastm1059a/m. WILLTHEArmorGalv COATINGSTICKTOFASTENERS? TheArmorGalv coatingactuallybecomespartofthesurfaceofthefastener!itnot onlycoats,itpenetrates(diffuses)intothesurface.theresultisahard(38 42Rc) superabrasionresistantcoatingthatcannoteasilyberemovedbymechanical means. WILLTOPCOATSADHERETOArmorGalv? Let me start by saying that ArmorGalv is NOT pure zinc. It is, in fact, layers (phases) of zinc/iron alloy. The automotive industry has been using a form of this type of galvanizing for body sheet metal that will be painted because of its proven superior adhesion to paints characteristic. It is known as Galvanneal, which results in better paint adhesion and corrosion resistance. ArmorGalv s surface is not smooth like that of bright electroplated zinc, but is rather geographic. This is demonstrated in the following photo:

4 This surface results in superior adhesion of paint, silicates or Xylan to the surface. This is why Bodycote, Int l of England uses ArmorGalv as a base for Xylan that is used in offshore oil well applications for BP, and other topcoats under the tradename of Sheraplex. When ArmorGalv is followed by a paint, it is designated as ArmorPLEX. ArmorPLEX YEAH,BUTCANArmorGalv REALLYTAKETHEHEAT? TheArmorGalv coatinghasgreatheatresistance.unlikeanyotherzincbased coating,thiscoatingcanwithstandcontinuousserviceof650degreesc. HOWENVIRONMENTALLYFRIENDLYISArmorGalv? TheArmorGalv ThermalDiffusionprocessgeneratespracticallyzerolandfill material,useshardlyanywaterandresultsinachromefreenon toxiccoating. ThiscouldmakeArmorGalv anattractiveadditiontoafastenermanufacturing operation. In2006theUSEPAawardedtheArmorGalv processitsprestigiousmvp 2 Award Themostvaluablenewtechnologyaward. 1 ISTHEREASPECIFICATIONCOVERINGArmorGalv COATING? TheArmorGalv coating iscoveredbythejustissuedastm1059a/mstandard. HEY,HOWMANYPEOPLEACTUALLYAPPLYArmorGalv? TherearecurrentlyaboutfortyArmorGalv installationsaroundtheworld.they rangefromconstructionfastenermanufacturerstocoatersof40 footlongoilwell suckertubes. OK BUTISTHEArmorGalv COATINGCOSTCOMPETITIVE? 1 SeeDavidFergusonofUSEPA:CleanTechEnvironPolicy(2006) ApproachingZeroDischarge DOI /s

5 TheArmorGalv processrequiresaverysmallinvestmentinpollutioncontrol equipmentandcosts.thearmorgalv processis alsoextremelyefficientinitsuse ofzincandrequirespracticallynowater.thesefactorscombinetomake ArmorGalv verycostcompetitivewithotherhighcorrosionresistantzincalloy processes. Anymorequestions?Ifso,then,pleasecontactusandwewillreplyrightaway. PleaselookattheComparisonChartonthenextpage.

6 COMPARISONCOATINGCHART Coating Thickness Range HotDip Mechanical Plating Dip/Spin Electro Plating ArmorGalv Thermal Diffusion Corrosion Resistanc e Unifo rm H2 Embritt lement Rece ss Fill Paint& Rubber Bonding Weldable Galling Heat Resistant Abrasion Resistant Moderate Poor Yes Yes Very Poor No Yes No Poor No No Moderate Poor No Yes Poor No Yes No Poor No No Glass Beads Moderate Poor No Yes Good No Yes No Very No No Poor Moderate Very Yes No Moderate No Yes No Poor No No togood Poor foralloys Excellent Excel lent No No Excellent Yes No Yes To1,000F Coat S/S Hard Excellent Yes Yes 38/4 2Rc

ArmorGalv. Thermal Diffusion Galvanizing. fi corrosion protection RoHS compliant ASTM - A1059 A/M

ArmorGalv. Thermal Diffusion Galvanizing. fi corrosion protection RoHS compliant ASTM - A1059 A/M DELNORTH Introduces: ArmorGalv Thermal Diffusion Galvanizing. Cost effective, environment-friendly fi corrosion protection RoHS compliant ASTM - A1059 A/M Winner of EPA S (NPPR) 2006 MVP 2 Award (Most