1、Designation: A 780/A 780M 09Standard Practice forRepair of Damaged and Uncoated Areas of Hot-DipGalvanized Coatings1This standard is issued under the fixed designation A 780/A 780M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, t
2、he 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 Department of Defense.1. Scope*1.1 This practice describes m
3、ethods 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 c
4、oating 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 withi
5、n 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 mu
6、tuallyagreeable 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 A 780) or in SI units (as A 780M).Inch-pound units and SI units are not necessarily exactequivalents. Wit
7、hin 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 responsibilityo
8、f 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:2A 902 Terminology Relating to Metallic Coated Steel Prod-uctsD 520 Specification for Zinc Dust Pigment2.2 S
9、ociety 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 Definitio
10、nsFor definitions of terms used in thispractice, refer to Terminology A 902.4. 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 s
11、hall 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 possessthe required properties and may be used to repair damagedgalvanized coatings, as fol
12、lows:1This 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, 2009. Published May 2009. Originallyapproved in 1980.
13、 Last previous edition approved in 2006 as A 780 01(2006).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.3Av
14、ailable from Society for Protective Coatings (SSPC), 40 24th St., 6th Floor,Pittsburgh, PA 15222-4656, http:/www.sspc.org.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United Stat
15、es.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 500F(230 to 2
16、60C), 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
17、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 usuallybased on organic binders, pre-mixed and formulated specifi-cally for use on steel surfaces. Paints containing zinc dust,
18、 withconcentrations of zinc dust in the range of 65 to 69 % or above92 % in the dried film, are considered equally effective for therepair of damaged galvanized coatings. The repair paint to beused shall be selected by the galvanizer, unless the purchaserspecifies a particular concentration or paint
19、 system. Corrosionresistance and service performance are very dependent on theproperties of the paint system, the extent of surface prepara-tion, and skills of individual applicators. Annex A2 describesthe use of paints containing zinc dust. Specification D 520describes the zinc dust component of th
20、ese paints.4.2.3 Sprayed ZincThis 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,
21、 procedures, and specifications in Refs. (1) through (4)(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 Cl
22、ean the surface to be reconditioned 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, f
23、irstremove all weld flux residue 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 750
24、F(400C), nor allow the surrounding 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 stickto deposit an evenly distributed layer of the zinc alloy. Whenpowdered zinc alloys are used
25、, sprinkle the powder on thecleaned, 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 fluxresidue by rinsing with water or wiping with a damp clot
26、h.A1.6 Take thickness measurements 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 se
27、rviceconditions. Experience shows 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 recond
28、itioned with paints containingzinc 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 f
29、ieldexposure 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 canA 780/A 780M 092
30、be effected, surface preparation 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
31、 thatcannot be removed by wire 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 app
32、licationemploying multiple 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 eit
33、her a mag-netic, electromagnetic, or eddy-current gage to ensure that theapplied coating is as specified in accordance with SSPC-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.
34、2 If the area to be reconditioned 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.A
35、3.4 To ensure that a smooth reconditioned 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
36、coating as soon as possibleafter 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
37、be previously agreed upon between 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 Int
38、ernational Conference on Hot Dip Galvanizing,Interlaken, June 1961, pp. 128141.(2) SSPC-Paint-20,“ Zinc Rich Coatings, Type I Inorganic, Type IIOrganic, Steel Structures Painting Council, 4400 Fifth Ave., Pitts-burgh, PA 15213, 1979.(3) MIL-P-21035 (Ships), Military Specification,“ Paint, High Zinc
39、DustContent, Galvanizing Repair, Amendment 1, U.S. GovernmentPrinting Office, Washington, DC, 1970.(4) “Recommended Practices for Fused Thermal Sprayed Deposits,American Welding Society, Inc., 550 N.W. LeJeune Rd., Miami, FL33135, 1975.SUMMARY OF CHANGESCommittee A05 has identified the location of s
40、elected changes to this standard since the last issue(A 780 01(2006) that may impact the use of this standard. (May 1, 2009)(1) Revised 1.4 and changed designation to make standardapplicable in both units.A 780/A 780M 093ASTM International takes no position respecting the validity of any patent righ
41、ts asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any
42、time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments wil
43、l receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by AST
44、M International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).A 780/A 780M 094
