iso12944大气腐蚀环境

ISO/EN12944MJM/19/07/97/GDPageNo.17/31/98Thisstandard,whichisbothanewInternationalStandardandaEuropeanStandard,hasbeengivenpositivevotesbyboththeInternationalandEuropeancommitteesandcannowproceedtobeingafullpublishedstandard.Itisunlikelythatthiswillbethecaseforallpartsuntilmid1998attheearliest.Itshouldbenoted,thatbecauseoftheapprovalgivenbytheEuropeancommittee,thisstandardwillreplaceexistingnationalstandardssuchasBS5493andDIN55928.ThemainproblemIseeatthemomentisthatitappearsunlikelythattheUSbasedspecifyinghouseswillusethespecification,butwillcontinuetouseSSPCandNACEguidelines.ISO12944statesthatitisdesignedforusebyengineerswhohavesometechnicalknowledgeintheareaofcorrosionprotection,aswellasknowledgeofotherrelevantspecifications.Manywillfindthedurabilityrangestobeextremelyuseful-thisistheestimatedtimetofirstmajormaintenance.ThisneedstobeagreedbetweentheinterestedpartieswithreferencetoISO4628/1toISO4628/5.ItshouldalwaysberealisedthatmuchlesseffortisrequiredtomaintainacoatingwhichhasbrokendowntoRi2thanonewhichhasbrokendowntoRi3,forexample.The‘durability’rangesconsideredare:-Low2-5YearsMedium5-15YearsHigh15YearsandareassumingthecoatinghasreachedabreakdownlevelofRi3.(Itisemphasisedthatthedurabilityrangeisnotaguaranteetime.Itispurelypresenttohelptheownerofthestructureestimatesensiblemaintenancetimes.Theguaranteetimeisgenerallyshorterthanthedurabilityrange,andthereisnosimplerelationshipbetweenthetwo.)ISO/EN12944MJM/19/07/97/GDPageNo.2SUMMARYSECTIONSISO12944-2Coversthecorrosivityofvariousenvironmentsandhowthesecanbemeasured.Variousanti-corrosivesystemscanthenbespecifiedfortheseenvironments.IS19244-3Dealswithbestpracticesinstructuralsteeldesignfromacorrosionpreventionviewpoint.ISO12944-4Coverssurfacepreparation-referencetoISO8501,IS08502,IS08503,ISO8504.ISO12944-5Typicalpaintsystemsbygenerictypeforagivendurabilityinagivenenvironment.ISO12944-6Laboratorytestingofpaintsystems,particularlyintendedforthosewheresufficientpracticalexperienceisnotyetavailable.Doesnotcoverpowertoolcleanedsteelspecifically.ISO12944-7Coversapplicationatworksoronsite,inspectionandfollowup.Alsodealswithreferenceareas.ISO12944-8Describeshowtopreparespecificationsforcorrosionprotectionandancillaryissues.ISO/EN12944MJM/19/07/97/GDPageNo.3PART2CLASSIFICATIONOFENVIRONMENTSDefinedfromweightlossofmetallic(lowcarbonsteelandzinc)specimensoveradefinedperiodof1year(notmoreandnotless).Thereareobviousdifferencesinthisapproachbecauseofchangeofclimateonayearlybasis,butthiscertainlyhelpsquantifythecorrosivityofanenvironment.ISO/EN12944MJM/19/07/97/GDPageNo.407May1997TABLE1-CORROSIVITYOFENVIRONMENTSExteriorInteriorD.F.T*C1,C2Verylow-low10-200g/m2(1.3-25µm)Heatedbuildings/neutralatmospheres.75µmRuralareas,lowpollution,dry.Unheatedbuildings,possiblecondensation200µmC3Medium200-400g/m2(25-50µm)UrbanandindustrialatmospheresModerateSO2pollutionModeratecoastalCl)Productionroomswithhighhumidityandairpollution200µmC4High40-650g/m2(50-80µm)Industrialandcoastal.Chemicalprocessingplants240µm(Zinc)280µm(Non-zinc)C5-IVeryhighindustrial650-1500g/m2Industrywithhighhumidityandaggressiveatmosphere320µmC5-MVeryhighmarine650-1500g/m2Marinecoastal,offshoreHighsalinity320µmI1StructuresimmersedinfreshwaterI2StructuresimmersedinseaorbrackishwaterI3Structuresimmersedinsoil(RefertoISO12944-2)*Abovethicknessesrefertomulti-coatsystems.Wheresinglecoatsareappliedhigherfilmthicknesseswillberequired(seerecommendedspecifications).ISO/EN12944MJM/19/07/97/GDPageNo.5PART3STRUCTURALDESIGNISO12944-3,whichcoversbasicdesigncriteria,isreallyoutsidethescopeofprotectivecoatingsmanufacturers.ThiscanonlyreallybefullyimplementedattheNewConstructionstageorbymajormodificationatalaterdate.Coatingsareoftenexpectedtoalleviate,orhelpalleviate,corrosionproblemsduetodesignerrors.Inthisinstance,itcouldwellbethatdifferentcoatingspecificationswouldberequiredfortheseareaswhichcouldbethicker/morecorrosionresistantthanthoseusedelsewhere.Typically,ifacertainareawassubjectedtofrequentpondingofrainwaterbecauseofdesign,theneithermodificationwouldberequiredtopreventthisoradifferentcoatingsystemcouldbeneeded.ISO/EN12944MJM/19/07/97/GDPageNo.6ISO12944-5PROTECTIVEPAINTSYSTEMSThissection,andthatontesting,arethosemostlikelytobearguedoverandtoprovidethegreatestareasofcontention.Intheareasofgenericpaintsystems,almosteverytypewhichcanbeimaginedhasbeencovered,andwhatappearstomeaseriesofquitecomplicatedmatriceshavebeenputtogether.Thisispossiblywhythispartofthespecificationisnotdueforcompletionuntil1998andwillbethelastsectionfinalised.Atthistimetherecontinuestobemuchdiscussiononthissection,andmodificationswillcertainlybemade.Currently,forexample,itisindicatedthatbothsolventbasedalkydsandwaterbasedacrylicswilldryat0ºC,certainlywewouldnotrecommendthistypeofconditionforwaterbased,andonconventionalalkydsIwouldexpectanextremelynegativeeffect.•Note,theproposeddefinitionandriderregardingzincrichcoatings.ThisnowbecomesmuchclosertotheSSPCSP20definitionthan,forexample,currentBritishStandards.•Minimumfilmthicknessshouldbe80%specifiedd.f.t.•Rec