1、Designation: A780/A780M 09 (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
2、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 pr
3、actice 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), i
4、n 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 a
5、re 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 lim
6、ited 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 exact
7、equivalents. 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
8、 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 Dus
9、t 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. Terminolog
10、y3.1 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 appl
11、ied 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 coa
12、tings, 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 t
13、o 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
14、. 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 p
15、age 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 liqu
16、idus 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
17、). 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 concen-trations of zinc d
18、ust in the range of 65 to 69 % or above 92 %in the dried film, are considered equally effective for the repairof damaged galvanized coatings. The repair paint to be usedshall be selected by the galvanizer, unless the purchaserspecifies a particular concentration or paint system. Corrosionresistance
19、and service performance are very dependent on theproperties of the paint system, the extent of surfacepreparation, and skills of individual applicators. Annex A2describes the use of paints containing zinc dust. SpecificationD520 describes the zinc dust component of these paints.4.2.3 Sprayed ZincThi
20、s method involves the applicationof a zinc coating by spraying the surface to be repaired withdroplets of molten metal using wire or ribbon, or powderprocesses. Annex A3 describes the use of sprayed zinc.4.3 For further information, reference may be made to thepapers, procedures, and specifications
21、in Refs. (1) through (2)(see list of references at the end of this practice).5. Keywords5.1 coatingszinc; galvanized coating repair; galvanizedcoatings; touch-up; zinc coating repair; zinc coatingsANNEXES(Mandatory Information)A1. REPAIR USING ZINC-BASED ALLOYSA1.1 Clean the surface to be reconditio
22、ned using a wirebrush, a light grinding action, or mild blasting. To ensure thata smooth reconditioned coating can be effected, surface prepa-ration shall extend into the surrounding, undamaged galva-nized coating.A1.2 If the area to be reconditioned includes welds, firstremove all weld flux residue
23、 and weld spatter (of a size thatcannot be removed by wire brushing or blast cleaning) bymechanical means, such as chipping, grinding, or powerscaling, etc.A1.3 Preheat the cleaned area to be reconditioned to at least600F (315C). Do not overheat the surface beyond 750F(400C), nor allow the surroundi
24、ng galvanized coating to beburned. Wire brush the surface to be reconditioned duringpreheating. Pre-flux, if necessary.A1.4 Rub the cleaned, preheated area with the repair stick todeposit an evenly distributed layer of the zinc alloy. Whenpowdered zinc alloys are used, sprinkle the powder on theclea
25、ned, preheated surface and spread out with a spatula orsimilar tool. The thickness of the applied coating shall be asagreed upon between the contracting parties.A1.5 When the repair has been effected, remove flux residueby rinsing with water or wiping with a damp cloth.A1.6 Take thickness measuremen
26、ts with either a magnetic,electromagnetic, or eddy-current gage to ensure that theapplied coating is as specified.A2. REPAIR USING PAINTS CONTAINING ZINC DUSTA2.1 Preparation of the damaged surface will be influencedby the type of paint selected and the anticipated serviceconditions. Experience show
27、s that in general, organic zinc-richsystems are tolerant of marginal surface preparation. Mostorganic paints containing zinc dust are not critical of climaticor atmospheric conditions for curing. The following generalguidelines shall apply:A2.1.1 Surfaces to be reconditioned with paints containingzi
28、nc dust shall be clean, dry, and free of oil, grease, preexistingpaint, and corrosion by-products.A2.1.2 Where anticipated, field service conditions includeimmersion, blast clean the surface in accordance with SSPC-SP10/NACE No. 2 near white metal. For less critical fieldA780/A780M 09 (2015)2exposur
29、e conditions, clean the surface to bare metal, inaccordance with SSPC-SP11, as a minimum. Where circum-stances do not allow blast or power tool cleaning, it ispermissible to hand tool areas clean in accordance withSSPC-SP2. To ensure that a smooth reconditioned coating canbe effected, surface prepar
30、ation shall extend into the undam-aged galvanized coating. The method and extent of surfacepreparation shall be mutually agreeable to the contractingparties.A2.1.3 If the area to be reconditioned includes welds, firstremove all weld flux residue and weld spatter (of a size thatcannot be removed by w
31、ire brushing or blast cleaning) bymechanical means, such as chipping, grinding, or powerscaling, etc.A2.1.4 Spray or brush-apply the paints containing zinc dustto the prepared area. Apply the paint as in accordance with themanufacturers printed instructions in a single applicationemploying multiple
32、passes to achieve a dry film thickness to beagreed upon between the contracting parties. Allow adequatecuring time before subjecting repaired items to service condi-tions in accordance with the manufacturers printed instruc-tions.A2.1.5 Take thickness measurements with either amagnetic, electromagne
33、tic, or eddy-current gage to ensure thatthe applied coating is as specified in accordance withSSPC-PA2.A3. REPAIR USING SPRAYED ZINC (METALLIZING)A3.1 Surfaces to be reconditioned by zinc metallizing shallbe clean, dry and free of oil, grease, and corrosion products.A3.2 If the area to be reconditio
34、ned includes welds, firstremove all flux residue and weld spatter of a size or type thatcannot be removed by blast cleaning by mechanical means,that is, chipping, etc.A3.3 Blast clean the surface to be reconditioned in accor-dance with SSPC-SP5/NACE No. 1, white metal.A3.4 To ensure that a smooth re
35、conditioned coating can beeffected, surface preparation shall be extended into the sur-rounding undamaged galvanized coating.A3.5 Apply the coating to the clean and dry surface bymeans of metal-spraying pistols fed with either zinc wire orzinc powder. Apply the sprayed coating as soon as possibleaft
36、er surface preparation and before visible deterioration of thesurface has occurred.A3.6 The surface of the sprayed coating shall be of uniformtexture, free of lumps, coarse areas, and loosely adherentparticles.A3.7 The nominal thickness of the sprayed zinc coatingshall be previously agreed upon betw
37、een the contractingparties.A3.8 Take thickness measurements with either a magnetic,electromagnetic, or eddy-current gage to ensure that theapplied coating is as specified.REFERENCES(1) Van Eijnsbergen, J. F. H., et al, “Reconditioning Damaged GalvanizedSurfaces, 6th International Conference on Hot D
38、ip Galvanizing,Interlaken, June 1961, pp. 128141.(2) “Recommended Practices for Fused Thermal Sprayed Deposits,American Welding Society, Inc., 550 N.W. LeJeune Rd., Miami, FL33135, 1975.(3) SSPC-Paint-20,“ Zinc Rich Coatings, Type I Inorganic, Type IIOrganic, Steel Structures Painting Council, 4400
39、Fifth Ave.,Pittsburgh, PA 15213, 1979.(4) MIL-P-21035 (Ships), Military Specification,“ Paint, High Zinc DustContent, Galvanizing Repair, Amendment 1, U.S. GovernmentPrinting Office, Washington, DC, 1970.A780/A780M 09 (2015)3ASTM International takes no position respecting the validity of any patent
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