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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The touch-up and repair of hot-dip galvanized steel coatings is important to maintain uniform barrier and cathodic protection as well as ensure longevity.
Ensuring Conformance to ASTM A780
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.
Touch-up and repair of galvanized steel is simple whether a7780 galvanized or in service for years.
The practice is the same, but there are more restrictions to the allowable repairs on a new product than one that has been in service.
The videos provide highly beneficial visual aids to those needing assistance with touch-up and repair, whether in the plant or the field.
ASTM A780-Zinc Dust in Paint
Topics include proper materials to use while performing the process, as well as specifications to follow and proper application of the repair materials. 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:. When it comes to repairing galvanized steel in the field, there is no limitation to the size that can be repaired.
The zinc coating is difficult to damage, and field fabrication that requires removal of the coating should be minimized as much as possible. 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.
A listing of various manufacturers and products for the maintenance and repair of hot-dip galvanized structures is available for download. The specification explains how to use the various repair methods as well as the required coating thickness for the repaired area.
Touch-up materials are required to meet a coating thickness of at least 2. ASTM A contains three acceptable methods of touch-up and repair of hot-dip galvanized steel: Soldering is done with zinc-based alloys in either a stick or powder form.
Ensuring Conformance to ASTM A | American Galvanizer’s Association
The area being repaired needs qstm be preheated to approximately F C. The repair coating thickness must meet the specification requirement for the material category of the part with a maximum thickness of 4 mils ?
Zinc-based solder products closely match the surrounding zinc and blend in well with the existing coating appearance. Zinc-rich paint is applied to a clean, dry ashm surface by either a brush or spray. Paints containing zinc dust are classified as organic or inorganic, depending on the binder they contain.
Inorganic binders are particularly suitable for paints applied in touch-up applications of undamaged hot-dip galvanized areas. Zinc spray, or metallizing, is done by melting zinc powder or zinc wire in a flame or electric arc and projecting the molten zinc droplets by air or gas onto the surface to be coated. The zinc used is nominally For best results, thickness measurements for the metallized coating should be taken with either a magnetic or an electromagnetic aa780.
ASTM AZinc Dust in Paint | American Galvanizer’s Association
Watch the Videos 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: Zinc-Rich Paints Zinc-rich paint is applied to a clean, dry steel surface by either a brush atsm spray.
Zinc Spray Metallizing Zinc spray, or metallizing, is done by melting zinc powder or zinc wire in a flame or electric arc and projecting the molten zinc droplets by air or gas onto the surface to be coated.
Inspector Listing – Non-U. Galv Touch Up Methods Dr.
Galv Touch-Up and Repair Dr. Galv What does the cold galvanizing process consist of?