This intmatial stndard was deeloped in accordance with internationally recegnieed principls on standardizati stablshed in the Decisio en Principles for the Developm ent of Internaticnal Standards Guides and Remcndations issned by the Woeld Trade Organization Technical Barriers to Trade (TBT) Comittee. Designation:A780/A780M-20 INTERNATIONAL StandardPracticefor RepairofDamagedandUncoatedAreasofHot-Dip GalvanizedCoatings This standard is isued under the fised designation A780VA780M; the nember immediately following the designaticn indicates the year of original adoption or in the case of revision the year of last revisicn. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revisicen or reaproval. This standnd hs bem approed for ase br agecier ef fhe U.S. Deprment of Dfene. 1. Scope ization established in the Decision on Principles for the 1.1 This practice describes methods that may be used to Development of Internarional Standards Guides and Re- repair damaged hot-dip galvanized coatings on hardware mendations issued by rhe World Trade Organization Techunical structural shapes and ther products fabricated prior to hotdip Barriers to Trade (TBT) Commiltee. galvanizing and uncoated areas remaining after initial hot-dip galvanizing. The damage may be the result of welding or 2. Referenced Documents cutting (flame) in which case the coating will be damaged 2.1 ASTM Standarnds:2 predominantly by burming. This practice can also be used to A902 Terminology Relating to Metallic Coated Steel Prod- ucts rough handing during shipping or erection. Requirements D520 Specification for Zinc Dust Pigment concerning the renovation of uncoated areas remaining after 2.2 SSPC Documents:3 initial hot-dip galvanizing are contained within the applicable SSPC-PA2 Measurement of Dry Paint Thickness with Mag- material specification. netic Gages 1.2 This practice describes the use of low melting point zinc SSPC-SP5/NACE No.I White Metal Blast Cleaning SSPC-SP2 Hand Tool Cleaning the use of paints containing zinc dust and the use of sprayed alloy repair rods or powders made specifically for this purpose SSPC-SPI0/NACE No.2 Near-White Blast Cleaning zinc (metallizing). SSPC-SPl11 Power Tool Cleaning to Bare Metal 1.3 The extent of repair shall be limited to an area mutually 3. Terminology agreeable to the contracting parties. Similarly contracting parties shall agree to the repair method to be used. 3.1 Definitions-For definitions of terms used in this practice refer to Terminology A902. either inch-pound units (as A780) or in SI units (as A780M). 4. Materials Inch-pound units and SI units are not necessarily exact equivalents. Within the text of this specification and where 4.1 ProperriesThe material used for repairs shall have the appropriate SI units are shown in brackets. Each system shall following characteristics: 4.1.1 One application of the material shall provide a coating be used independently of the other without bining values in thickness of at least 2.0 mils [50.8 μm]. any way. 4.1.2 The applied coating shall provide barrier protection 1.5 This standard does not purport to address all of the and shall preferably be anodic to steel. safety concems if any. associated wizth its use. lt is the 4.1.3 Application of the coating material shall be possible responsibiliry of the user of this standard to establish appro- under shop or field conditions. priate safety health and environmental practices and deter- 4.2 7ypesThere are three types of material that possess the mine the applicabiliry of regulatory limitations prior to use. 1.6 This intermational stondord was developed in accor- required properties and may be used to repair damaged dance wirh intermationally recognized principles on stancdard- galvanized coatings as follows: This peactice is under the jurisdiction of ASTM Committee A05 on Metallic- For referenced ASTM standards visit the ASTM website .astm.org or Coated Iron and Steel Products and is the direct responsibility of Submite A05.13 on Structural Shapes and Hardware Specifications. Standrds volume information refer to the standard’s Document Summary page on contact ASTM Customer Service at service@astm.oeg. For Annol Book of ASTM Suuo oo aquadg papsnd 0coe 1 das podde up m approved in 1980. Last previous edition approved in 2015 as A780/ Ptsburgh PA 15222-4656 htp//ww.sspc.org. Available from Society foe Protective Costings (SSPC) 40 24th St 6th Floor A780M 09(2015). DOI: 10.1520/A0780_A0780M-20. Copyright 0 ASTM Intematfonal 100 Bar Hartor Orive PO Box C700 West Conshohocken PA 19428-2959. United Stalte 1
A780/A780M-20 4.2.1 Zinc-Based SoldersZinc alloy solders are to be used shall be selected by the galvanizer unless the purchaser for repairs. The most mon types of solders are zinc- specifies a particular concentration or paint system. Corosion cadmium zinc-tin-lead and zinc-tin-copper alloys. Zinc- resistance and service performance are very dependent on the cadmium and zinc-tin-lead alloys have liquidus temperatures in properties of the paint system the extent of surface the ranges from 518 to 527 °F [270 to 275 °C] and 446 to preparation and skills of individual applicators. Annex A2 500 °F [230 to 260 °C] respectively. (The liquidus temperature describes the use of paints containing zinc dust. Specification is that temperature above which an alloy is pletely molten.) D520 describes the zinc dust ponent of these paints. The zinc-tin-copper alloys have a liquidus temperature in the 4.2.3 Sprayed Zinc-This method involves the application range from 660 to 670 °F [349 to 354 °C] but they are applied of a zinc coating by spraying the surface to be repaired with while in a semisolid state in the preferred application tempera- droplets of molten metal using wire or ribbon or powder os 00 00 00 u am processes. Annex A3 describes the use of sprayed zinc. be used in rod form or as powders. Annex A1 describes the use spos paseq-ouz go 4.3 For further information reference may be made to the 4.2.2 Pcints Contcining Zinc DustThese are usually based papers procedures and specifications in Refs (1-4) (see list of on organic binders pre-mixed and formulated specifically for references at the end of this practice). use on steel surfaces. Paints containing zinc dust with concen- trations of zinc dust in the range of 65 to 69 % or above 92 % 5. Keywords in the dried film are considered equally effective for the repair 5.1 coatings-zinc; galvanized coating repair; galvanized of damaged galvanized coatings. The repair paint to be used coatings; touch-up; zinc coating repair; zinc coatings ANNEXES (Mandatory Information) A1. REPAIR USING ZINC-BASED ALLOYS A1.1 Clean the surface to be reconditioned using a wire A1.4 Rub the cleaned preheated area with the repair stick to brush a light grinding action or mild blasting. To ensure that a smooth reconditioned coating can be effected surface prea- deposit an evenly distributed layer of the zinc alloy. When ration shall extend into the surrounding undamaged galva- powdered zinc alloys are used sprinkle the powder on the nized coating. cleaned preheated surface and spread out with a spatula or similar tool. The thickness of the applied coating shall be as A1.2 If the area to be reconditioned includes welds first agreed upon between the contracting parties. remove all weld flux residue and weld spatter (of a size that cannot be removed by wire brushing or blast cleaning) by A1.5 When the repair has been effected remove flux residue mechanical means such as chipping grinding. or power by rinsing with water or wiping with a damp cloth. scaling etc. A1.6 Take thickness measurements with either a magnetic A1.3 Preheat the cleaned area to be reconditioned to at least electromagnetic or eddy-current gauge to ensure that the 600 °F [315 °C]. Do not overheat the surface beyond 750 °F applied coating is as specified. [400 °C] nor allow the surrounding galvanized coating to be bumed. Wire brush the surface to be reconditioned during preheating. Pre-fux if necessary.
ASTM-A780/A780M-20 Standard Practice for Repair of Damaged and Uncoated Areas of Hot-Dip Galvanized Coatings.pdf
