esignation:A780-01 StandardPracticefor RepairofDamagedandUncoatedAreasofHot-Dip GalvanizedCoatings1 jo e q sp u q u ppu qun a 0 ueup pg aq pss s pepus s original dptin or inthe ase of revisin te yea of last revisin A mber in pares idates the yr f lat rapl. superscript epsilon (e) indicates an editorial change since the last revision or reapproral. This standored har been opproved for ase bhy agencies ef the Deprrtment ef Defense. 1. Scope SSPC-PA2 Measurement of Dry Paint Thickness with Mag- 1.1 This practice describes methods which may be used to netic Gages repair damaged hot-dip galvanized coatings on hardware SSPC-SP2 Hand Tool Cleaninga structural shapes and other products fabricated prior to hot-dip SSPC-SP10/NACE No.2 Near-White Blast Cleaning4 SSPC-SP5/NACE No.1 White Metal Blast Cleaning* galvanizing and uncoated areas remaining after initial hot-dip galvanizing. The damage may be the result of welding or SSPC-SP11 Power Tool Cleaning to Bare Metal* cutting (flame) in which case the coating will be damaged predominantly by burming. This practice can also be used to 3. Terminology repair hot-dip galvanized coatings damaged by excessively 3.1 Definirions-For definitions of terms used in this rough handling during shipping or erection. Requirements practice refer to Terminology A 902. concerning the renovation of uncoated areas remaining after initial hot-dip galvanizing are contained within the applicable 4. Materials material specification. 4.1 ProperiesThe material used for repairs shall have the 1.2 This practice describes the use of low melting point zinc following characteristics: alloy repairods or powdersmade specifically for this pupose 4.1.1 One application of the material shall provide a coating the use of paints containing zinc dust and the use of sprayed thickness of at least 2.0 mils (50.8 μm). zinc (metallizing). 4.1.2 The applied coating shall provide barrier protection 1.3 The extent of repair shall be limited to an area mutually and shall preferably be anodic to steel. agreeable to the contracting parties. Similarly contracting 4.1.3 Application of the coating material shall be possible parties shall agree to the repair method to be used. under shop or field conditions. 1.4 This standard does not purport to address the sofery 4.2 TypesThere are three types of materal that possess problems if any associated with its use. Ir is the responsibiliry the required properties and may be used to repair damaged of the user of this standord to establish appropriate safery cnd galvanized coatings as follows: heaith practices and determine the applicabiliry ofregulatory 4.2.1 Zinc-Based SoldersZinc alloy solders are to be used limirations prior to use. for repairs. The most mon types of solders are zinc- 1.5 The values stated in inch-pound units are to be regarded cadmium zinc-tin-lead and zinc-tin-copper alloys. Zinc- as the standard. The values given in parentheses are for cadmium and zinc-tin-lead alloys have liquidus temperatures in information only. (230 to 260°C) respectively. (The liquidus temperature is that the ranges from 518 to 527°F (270 to 275°C) and 446 to 500°F 2. Referenced Documents temperature above which an alloy is pletely molten.) The 2.1 ASTM Standards: zinc-tin-copper alloys have a liquidus temperature in the range A 902 Teminology Relating to Metallic Coated Steel Prod- from 660 to 670°F (349 to 354°C) but they are applied while ucts2 in a semisolid state in the preferred application temperature D 520 Specification for Zinc Dust Pigment range from 480 to 570°F (250 to 300°C). The solders can be 2.2 Sociery for Protective Coatings (SSPC) Documents: used in rod form or as powders. Annex A1 describes the use of zinc-based solders. 4.2.2 Paints Containing Zinc DustThese are usually This prctioe is under the jurisditio of ASTM Commite A5 on Metallic based on organic binders pre-mixed and formulated specifi- Coated Iron and Stl Prodts an is the diret responsibility of Submmitee cally for use on steel surfaces. Paints containing zinc dust with A05.13 on Structeal Shapes and Hardare Specifications. concentrations of zinc dust in the range of 65 to 69 % or above published as A 780 80. Last previous edition A 780 00. qeuuo 1og oug ppnd 1oo o1 lady paadde oa un 2 Amal Boot ef ASTM Sndonds Vol 01.06. ^Aralable fm Steel Stuctures Painting Conil 4400 Ffth Ave. Ptsbrgh * Aomaal Booe of AST3M Stdrds Vol 06.03. PA 15213. Copyright @ ASTM 100 Barr Hartor Drive Wiest Conshohocken PA 19428-2959 United States.
A780 92 % in the dried film are considered equally effective for the droplets of molten metal using wire or ribbon or powder used shall be selected by the galvanizer uless the purchaser repair of damaged galvanized coatings. The repair paint to be processes. Annex A3 describes the use of sprayed zinc. specifies a particular concentration or paint system. Corrosion 4.3 For further information reference may be made to the resistance and service performance are very dependent on the papers procedures and specifications in Refs. (1 through (4) properties of the paint system the extent of surface prepara- (see list of references at the end of this practice). tion and skills of individual applicators. Annex A2 describes the use of paints containing zinc dust. Specification D 520 5. Keywords describes the zinc dust ponent of these paints. 5.1 coatings-zinc; galvanized coating repair; galvanized 4.2.3 Sprayed Zinc-This method involves the application coatings; touch-up; zinc coating repair; zinc coatings of a zinc coating by spraying the surface to be repaired with ANNEXES (Mandatory Information) A1. REPAIR USING ZINC-BASED ALLOYS A1.1 Clean the surface to be reconditioned using a wire bumed. Wire brash the surface to be reconditioned during brush a light grinding action or mild blasting. To ensure that preheating. Pre-flux if necessary. a smooth recondiioned coating canb ffected surface ration shall extend into the surrounding undamaged galva- A1.4 Rub the cleaned preheated area with the repair stick nized coating. to deposit an evenly distributed layer of the zinc alloy. When powdered zinc alloys are used sprinkle the powder on the A1.2 If the area to be reconditioned includes welds first cleaned preheated surface and spread out with a spatula or remove all weld flux residue and weld spatter (of a size that similar tool. The thickness of the applied coating shall be as cannot be removed by wire brushing or blast cleaning) by agreed upon between the contracting parties. mechanical means such as chipping grinding or power A1.5 When the repair has been effected remove fux scaling etc. o duep e qm Sum no 1aem qm Susu Aq onpisn A1.3 Preheat the cleaned area to be reconditioned to at least A1.6 Take thickness mcasurements with either a magnetic 600°F (315°C). Do not overheat the surface beyond 750°F (400°C) nor allow the surrounding galvanized coating to be electromagnetic or eddy-current gage to ensure that the applied coating is as specified. A2. REPAIR USING PAINTS CONTAINING ZINC DUST A2.1 Preparation of the damaged surface will be influenced aged galvanized coating. The method and extent of surface by the type of paint selected and the anticipated service preparation shall be mutually agreeable to the contracting conditions. Experience shows that in general organic zinc-rich parties. systems are tolerant of marginal surface preparation. Most A2.1.3 If the area to be reconditioned includes welds first or atmospheric conditions for curing. The following general organic paints containing zinc dust are not critical of climatic remove all weld flux residue and weld spatter (of a size that cannot be removed by wire brushing or blast cleaning) by guidelines shall apply: mechanical means such as chipping grinding. or power A2.1.1 Surfaces to be reconditioned with paints containing scaling etc. zinc dust shalle clean dy and free f il grease pexistn A2.1.4 Spray or brush-apply the paints containing zinc dust paint and corrosion by-products. to the prepared area. Apply the paint as in accordance with the manufacturer’s printed instructions in a single application immersion blast clean the surface in accordance with SSPC- employing multiple passes to achieve a dry film thickness to be SP10/NACE No. 2 near white metal. For less critical field agreed upon between the contracting parties. Allow adequate exposure conditions clean the surface to bare metal in curing time before subjecting repaired items to service condi accordance with SSPC-SP11 as a minimum. Where circum- tions in accordance with the manufacturer’s printed instruc- stances do not allow blast or power tool cleaning it is tions. A2.1.5 Take thickness measurements with either a mag- SSPC-SP2. To ensure that a smooth reconditioned coating can netic electromagnetic or eddy-current gage to ensure that the be effected surface preparation shall extend into the undam- applied coating is as specified in accordance with SSPC-PA2. 2
A780 A3. REPAIR USING SPRAYED ZINC (METALLIZING) A3.1 Surfaces to be reconditioned by zinc metallizing shall zinc powder. Apply the sprayed coating as soon as possible be clean dry and free of oil grease and corrosion products. after surface preparation and before visible deterioration of the A3.2 If the area to be reconditioned includes welds first surface has occurred. remove all fux residue and weld spatter of a size or type that cannot be removed by blast cleaning by mechanical means A3.6The surface of the sprayed coating shall be of uniform that is chipping etc. texture free of lumps coarse areas and loosely adherent particles. A3.3 Blast clean the surface to be reconditioned in accor- dance with SSPC-SP5/NACE No. 1 white metal. A3.7T The nominal thickness of the sprayed zinc coating A3.4 To ensure that a smooth reconditioned coating can be shall be previously agreed upon between the contracting effected surface preparation shall be extended into the sur- parties. rounding undamaged galvanized coating. A3.8 Take thickness measurements with either a magnetic A3.5 Apply the coating to the clean and dry surface by electromagnetic or eddy-current gage to ensure that the means of metal-spraying pistols fed with either zinc wire or applied coating is as specified. REFERENCES (I) Van Eijnsbergen J. F. H et al Reconditioning Damaged Galvanized s (3) MIL-P-21035 (Ships) Military Specification " Paint High Zinc Dust Content Galvanizing Repair " Amendment 1 U.S. Government Interlaken June 1961 pp. 128141. Printing Office Washington DC 1970. (4) “Remended Practices for Fused Thermal Sprayed Deposits " Organic Steel Structures Painting Council 4400 Fifth Ave. Pitts- American Welding Society Inc. 550 N.W. LeJeune Rd. Miami FL burgh PA 15213 1979. 33135 1975. psufuAad ou pueugu Xqsuodsas umo sa (puue ave sufy qons jo yuufuur μo xsu au pue sufy uayed wh ay e mentedin s standard. Users of mis stndard are expessy aised fha dteminatio of the vafdy of ary suh f revsed taprvdwtrYurcmns areidetfrvisf sstndadrfrain/sanas This stanrd s sject foevisin a ay me by hereponsble echical mmttee anmusterevewed evey five year and ang shoufd be adresed to ASTM Headguarters. Your ments w receive carefu consideration af a meeting of phe esponsib techica mitee whh youmay altend. f you fee/ fha your ments have not receved a far hearing you should make you views know to the ASTM Commitee on Standerds af the address shown beiow. 610-832-9585 (phone) 610-832-9555 (lax) er service@Pastm.org (e-mai); or through me ASTM website (.astm.org). mdivcuaf reprints (single or mulfipie cpies) of mis standard may be obtaned by contacting ASTM ar the above address or at
ASTM-A780-01 Standard Practice for Repair of Damaged and Uncoated Areas of Hot-Dip Galvanized Coatings.pdf
