ASTM A Practice for Repair of Damaged and Uncoated Areas of Hot-Dip Galvanized Coatings details how to repair a damaged hot-dip galvanized coating . 2. Referenced Documents. ASTM Standards: A Terminology Relating to Metallic Coated Steel Prod- ucts2. D Specification for Zinc Dust Pigment3. ASTM Designation: A (American Standard Testing Method). Standard Practice for Repair of Damaged and Uncoated Areas of Hot-Dip Galvanized Coatings.
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Although the hot-dip galvanized coating is very resistant to damage, small voids or defects in the coating can occur during the galvanizing process or due to improper handling of the steel after galvanizing.
A listing of various manufacturers and products for the maintenance and repair of hot-dip galvanized structures is available for download. Where circumstances do not allow blast cleaning, it is permissible to power disk sand areas to be repaired to bright metal.
Historical Version s – view previous versions of standard. Call for more information. Similarly, contracting parties shall agree to the repair method to be used. The method and extent of surface preparation shall be mutually agreeable to the contracting asmt. The videos provide highly beneficial visual aids to those needing assistance with touch-up and repair, whether in the plant or the field. This abstract is a brief summary of the referenced standard.
The repair coating thickness must meet the specification requirement for the material category of the part with a maximum thickness of 4 mils qstm When ready to perform mechanical cleaning, check the surface preparation standard for a7800 on the allowable tooling methods. Touch-up materials are required to meet a coating thickness of at least 2. Inspector Listing – Non-U. Therefore, once in-field, any size of repairable aetm defect can be touched up.
August 1, Authored by Alana Hochstein. For best results, thickness atm for the metallized coating should be taken with either a magnetic or an electromagnetic gauge.
ASTM AZinc Dust in Paint | American Galvanizer’s Association
Paints containing zinc dust are classified as organic or inorganic, depending on the binder they contain. It is informational only and not an asfm part of the standard; the full text of the standard itself must be referred to for its use and application.
The six-part video series will provide highly beneficial visual aids to those needing assistance with meeting the requirements of ASTM A The material used for repair shall have the specified coating thickness, shall provide barrier protection and preferably be anodic to steel, and application of the coating shall be possible under shop or field conditions.
Any dust or loose residue from cleaning must be brushed away using a stiff-bristle brush or blown off using clean, dry air. Each system shall be used independently of the other without combining values in any way. Brite Zinc is an organic zinc compound.
Repairing HDG Steel | American Galvanizer’s Association
The damage may be the result of welding or cutting flamein which case the coating will be damaged predominantly by burning. Galv Touch Up Methods Dr. It is important to note that the size restrictions apply to the astk s to be repaired prior to surface preparation.
When it comes to repairing galvanized steel in the field, there is no limitation to the size that can be repaired. Zinc-Rich Paints Zinc-rich paint is applied to a clean, dry steel surface by either a brush or spray.
Watch the Videos The main restriction in the specification for repairing newly galvanized material is the size of the area which is outlined a870 the product galvanizing specifications: After surface preparation, the standards refer to points of inspection necessary to ensure proper adhesion of the repair material.
For power tool cleaned surfaces, a surface profile depth micrometer is the appropriate method for confirming profile, unless otherwise agreed. In order a80 ensure strict adherence to the specification ASTM A when performing repairs at the galvanizing plant, the galvanizer should be well versed in the equipment, materials and surface preparation standards required of each repair method. Appropriate grinding tools include reciprocating sanders, orbital sanders, or grinding devices that utilize abrasive cloths, discs, wheels or flaps.
Ensure a blotter test is performed prior to using a compressed air source in accordance with Atsm D The area being repaired needs to be preheated to approximately F C. To ensure that a smooth reconditioned coating can be asfm, surface preparation shall extend into the undamaged galvanized coating.
However, do not clean excessively beyond the area of repair. Within the text of this specification and where appropriate, SI units are astn in brackets. Correct for the additional tape thickness i. The main restriction in the specification for repairing newly galvanized material is the size of the area which is outlined in the product galvanizing specifications:.
As noted before, the cathodic protection of the coating will provide some protection to uncoated areas, but the best practice for longevity is to touch-up any bare areas.
Ensuring Conformance to ASTM A780
Maximum Allowable Repair Size The practice for repairing the galvanized coating in-field is the same as the practice for repair at the galvanizing facility, but there are more restrictions to the allowable repair size while at the galvanizing facility. Where blast or power tool cleaning cannot be performed, hand tool cleaning per SSPC-SP2 Hand Tool Cleaning allows the use of wire aztm, scraping, chipping and sanding.
This practice describes methods that may be used to repair damaged hot-dip galvanized coatings on hardware, structural shapes, and other products fabricated prior to hot-dip galvanizing, and uncoated areas remaining after initial hot-dip galvanizing.
Surface Preparation Always check for visible contaminants on the surface of the repair area just prior to mechanical cleaning.
Hand tool cleaning with a stiff-bristle or nylon brush does not meet specification.