ASTM_D_6386_-_10.pdf

Designation:D638610Standard Practice forPreparation of Zinc(Hot-Dip Galvanized)Coated Iron andSteel Product and Hardware Surfaces for Painting1This standard is issued under the fixed designation D6386;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1.Scope*1.1 This practice describes methods of preparing surfaces ofnew and weathered hot-dip galvanized steel for painting.Hot-dip galvanized steel is produced by the immersion offabricated or unfabricated products in a bath of molten zinc,asspecified in Specifications A123/A123M or A153/A153M.This practice covers surface preparation on iron and steelproducts and hardware that have not been painted previously.Galvanized surfaces may have been treated with protectivecoatings to prevent the occurrence of wet storage stain.Thispractice does not apply to sheet galvanized steel products norto the coil coating or continuous roller coating processes.Sheetand coil surface preparation can be done in accordance withPractice D7396.1.2 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and to determine theapplication of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2A123/A123M Specification for Zinc(Hot-Dip Galvanized)Coatings on Iron and Steel ProductsA153/A153M Specification for Zinc Coating(Hot-Dip)onIron and Steel HardwareA780 Practice for Repair of Damaged and Uncoated Areasof Hot-Dip Galvanized CoatingsB201 Practice for Testing Chromate Coatings on Zinc andCadmium SurfacesD7396 Guide for Preparation of New,Continuous Zinc-Coated(Galvanized)Steel Surfaces for PaintingE376 Practice for Measuring Coating Thickness byMagnetic-Field or Eddy-Current(Electromagnetic)Test-ing Methods2.2 Society for Protective Coatings Specifications:3Surface Preparation Specification No.1 Solvent CleaningSurface Preparation Specification No.2 Hand Tool CleaningSurface Preparation Specification No.3 Power Tool Clean-ingSurface Preparation Specification No.7 Brush-Off BlastCleaningSurface Preparation Specification No.11 Power Tool Clean-ing to Bare MetalPaint Specification No.27Basic Zinc Chromate-VinylButyral Wash Primer3.Summary of Practice3.1 This practice describes the preparation methods thatprovide clean and suitable galvanized surfaces for painting,specifically so that an applied coating system can develop theadhesion necessary for a satisfactory service life.3.2 The zinc coating is constantly in a state of change.Fromthe time the steel part is removed from the galvanizing kettle,the exposed zinc coating interacts with the environment toform,first zinc oxides,next zinc hydroxides,and then zinccarbonates.4The process of complete conversion of the outerlayer of zinc carbonates can take up to two years of exposureto the environment,depending on the local climatologicalconditions.During the first stage,known as newly galvanizedsteel,the exposed surface consists mainly of zinc metal with asmall amount of zinc oxide.During the second stage,known aspartially weathered galvanized steel,the exposed surface1This practice is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.46 on Industrial Protective Coatings.Current edition approved July 1,2010.Published July 2010.Originally approvedin 1999.Last previous edition approved in 2005 as D6386 99(2005).DOI:10.1520/D6386-10.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available from Society for Protective Coatings(SSPC),40 24th St.,6th Floor,Pittsburgh,PA 15222-4656,http:/www.sspc.org.4This interaction is described in“Duplex Systems,”van Eijnsbergen,J.F.H.,Elsevier Science,New York,NY 1994,and in Zinc Handbook,Porter,F.,MarcelDekker,Inc.,New York,NY 1991.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 consists mainly of zinc oxides and zinc hydroxides with somezinc carbonates.At the final stage,known as weatheredgalvanized steel,the exposed surface consists mainly ofwater-insoluble zinc carbonates,some zinc oxides,and rarely,zinc hydroxides.The surface preparation for each of thesestages must be treated separately.3.3