ASTM_A_780_-_A_780M_-_09_2015.pdf

Designation:A780/A780M09(Reapproved 2015)Standard Practice forRepair of Damaged and Uncoated Areas of Hot-DipGalvanized Coatings1This standard is issued under the fixed designation A780/A780M;the number immediately following the designation indicates the yearof original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This practice describes methods that may be used torepair damaged hot-dip galvanized coatings on hardware,structural shapes,and other products fabricated prior to hot-dipgalvanizing,and uncoated areas remaining after initial hot-dipgalvanizing.The damage may be the result of welding orcutting(flame),in which case the coating will be damagedpredominantly by burning.This practice can also be used torepair hot-dip galvanized coatings damaged by excessivelyrough handling during shipping or erection.Requirementsconcerning the renovation of uncoated areas remaining afterinitial hot-dip galvanizing are contained within the applicablematerial specification.1.2 This practice describes the use of low melting point zincalloy repair rods or powders made specifically for this purpose,the use of paints containing zinc dust,and the use of sprayedzinc(metallizing).1.3 The extent of repair shall be limited to an area mutuallyagreeable to the contracting parties.Similarly,contractingparties shall agree to the repair method to be used.1.4 This specification is applicable to orders in eitherinch-pound units(as A780)or in SI units(as A780M).Inch-pound units and SI units are not necessarily exactequivalents.Within the text of this specification and whereappropriate,SI units are shown in brackets.Each system shallbe used independently of the other without combining values inany way.1.5 This standard does not purport to address the safetyproblems,if any,associated with its use.It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2.Referenced Documents2.1 ASTM Standards:2A902 Terminology Relating to Metallic Coated Steel Prod-uctsD520 Specification for Zinc Dust Pigment2.2 Society for Protective Coatings(SSPC)Documents:3SSPC-PA2 Measurement of Dry Paint Thickness with Mag-netic GagesSSPC-SP2 Hand Tool CleaningSSPC-SP5/NACE No.1 White Metal Blast CleaningSSPC-SP10/NACE No.2 Near-White Blast CleaningSSPC-SP11 Power Tool Cleaning to Bare Metal3.Terminology3.1 DefinitionsFor definitions of terms used in thispractice,refer to Terminology A902.4.Materials4.1 PropertiesThe material used for repairs shall have thefollowing characteristics:4.1.1 One application of the material shall provide a coatingthickness of at least 2.0 mils(50.8 m).4.1.2 The applied coating shall provide barrier protectionand shall preferably be anodic to steel.4.1.3 Application of the coating material shall be possibleunder shop or field conditions.4.2 TypesThere are three types of material that possess therequired properties and may be used to repair damagedgalvanized coatings,as follows:4.2.1 Zinc-Based SoldersZinc alloy solders are to be usedfor repairs.The most common types of solders are zinc-cadmium,zinc-tin-lead,and zinc-tin-copper alloys.Zinc-cadmium and zinc-tin-lead alloys have liquidus temperatures inthe ranges from 518 to 527F(270 to 275C)and 446 to 500F1This practice is under the jurisdiction of ASTM Committee A05 on Metallic-Coated Iron and Steel Products and is the direct responsibility of SubcommitteeA05.13 on Structural Shapes and Hardware Specifications.Current edition approved May 1,2015.Published May 2015.Originallyapproved in 1980.Last previous edition approved in 2009 as A780 09.DOI:10.1520/A0780_A0780M-09R15.2For 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(230 to 260C),respectively.(The liquidus temperature is thattemperature above which an alloy is completely molten.)Thezinc-tin-copper alloys have a liquidus temperature in the rangefrom 660 to 670F(349 to 354C),but they are applied whilein a semisolid state in the preferred application temperaturerange from 480 to 570F(250 to 300C).The solders can beused in rod form or as powders.Annex A1 describes the use ofzinc-based solders.4.2.2 Paints Containing Zinc DustThese are usually basedon organic binders,pre-mixed and formulated specifically foruse on steel surfaces.Paints containing zinc dust,with c