ASTM_D_7803_-_12.pdf

Designation:D780312Standard Practice forPreparation of Zinc(Hot-Dip Galvanized)Coated Iron andSteel Product and Hardware Surfaces for Powder Coating1This standard is issued under the fixed designation D7803;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.1.Scope1.1 This practice describes methods of preparing surfaces ofhot-dip galvanized iron and steel for powder coating and theapplication of powder coating materials.1.1.1 Powder coating is a dry finishing process which usesfinely ground particles of pigment and resin,electrostaticallycharged,and sprayed onto a part to be coated.The parts areelectrically grounded so that the charged particles projected atthem adhere to the surface and are held there until melted andfused into a smooth coating in the curing oven.1.1.2 Hot-dip galvanized iron or steel is produced by theimmersion of fabricated or un-fabricated products in a bath ofmolten zinc,as specified in Specification A123/A123M orA153/A153M.This practice covers surface preparation andthermal pretreatment of iron and steel products and hardwarewhich have not been painted or powder coated previously(Practice D6386).Galvanized surfaces may have been treatedwith protective coatings to prevent the occurrence of wetstorage stain.This practice neither applies to sheet galvanizedsteel products nor to the coil coating or continuous rollercoating processes.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 determine the applica-bility 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 SurfacesD4285 Test Method for Indicating Oil or Water in Com-pressed AirD6386 Practice for Preparation of Zinc(Hot-Dip Galva-nized)Coated Iron and Steel Product and HardwareSurfaces for PaintingD7091 Practice for Nondestructive Measurement of DryFilm Thickness of Nonmagnetic Coatings Applied toFerrous Metals and Nonmagnetic,Nonconductive Coat-ings Applied to Non-Ferrous MetalsE376 Practice for Measuring Coating Thickness byMagnetic-Field or Eddy-Current(Electromagnetic)Test-ing MethodsF21 Test Method for Hydrophobic Surface Films by theAtomizer Test2.2 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.12 Surface Prepara-tion and Cleaning of Metals by Water-Jetting Prior toRecoatingSurface Preparation Specification No.16 Brush-Off BlastCleaning of Coated and Uncoated Galvanized Steel,Stainless Steels,and Non-Ferrous Metals3.Summary of Practice3.1 This practice describes the procedures that can be usedto prepare surfaces for powder coating application on new,partially weathered,and fully weathered zinc-coated surfaceson after-fabrication iron and steel products.These procedures1This 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 June 1,2012.Published June 2012.DOI:10.1520/D7803-12.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 improve the bond of the powder coating to the zinc surfaceproviding for long life.3.2 The proper preparation of galvanized surfaces prior toapplication of powder coating is dependent on cleaning,profiling,and thermal pretreatment.4.Significance and Use4.1 This practice describes the methods of preparation ofhot-dip galvanized surfaces prior to the application of powdercoating.The key to achieving proper adhesion between powdercoatings and galvanized steel is surface preparation.Thesurface must be entirely free from metal oxides prior to powdercoating.Any metal oxides tha