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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As qstm 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. 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.
Repairing HDG Steel | American Galvanizer’s Association
Contact Us Order Status. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application. Where circumstances do not allow blast cleaning, it is permissible to power disk sand areas to be repaired to bright metal. Most organic zinc-rich paints are not critical of climatic or atmospheric conditions for curing.
For less critical field exposure conditions, blast clean the surface to near-white metal, in accordance with SSPC-SP10 1 to 2 mil 25 to 50 m anchor patternas a minimum. This practice describes the use of three types of material that possess the required properties for repair of damaged galvanized coatings, namely: 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.
This abstract is a brief summary of the referenced standard. Galv What does the cold galvanizing process consist of? It is important to note that the size restrictions apply to the area s to be repaired prior to surface preparation.
August 1, Authored by Alana Hochstein. Zinc-based solder products closely match the surrounding zinc and blend in well with the existing coating appearance.
This material provides general a7800 only and is not intended as a substitute for competent professional examination and verification as to suitability and applicability. This practice can aetm be used to repair hot-dip galvanized coatings damaged by excessively rough handling during shipping or erection. 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.
At the galvanizing facility, the maximum allowable repair size for iron and steel products per ASTM A is no more than 1 inch [2. Corrosion resistance and service performance are very dependent on the properties of the paint system, the extent of surface preparation, and skills of individual applicators.
The touch-up and repair of hot-dip galvanized steel coatings is important to maintain uniform barrier and cathodic protection asmt well as ensure longevity. However, do not clean excessively beyond the area of repair.
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.
Similarly, contracting parties shall agree to the repair method to be used. Each system shall be used independently of the other without combining values in any way.
ASTM A780-Zinc Dust in Paint
The specification explains how to use the various repair methods as well as the required coating thickness for the repaired area.
Zinc-Rich Paints Zinc-rich paint is applied to a clean, dry steel surface by either a brush or spray. The repair coating thickness must meet the specification requirement for asmt material category of the part with a maximum thickness of 4 mils ? The material provided herein has been 7a80 to provide accurate and authoritative information about after-fabrication hot-dip galvanized steel.
Paints containing zinc dust are classified as organic or inorganic, depending on the binder they contain. To ensure that a smooth reconditioned coating can be effected, surface preparation shall extend into the undamaged galvanized coating.
Ensuring Conformance to ASTM A | American Galvanizer’s Association
Effective May 1st Link to Active This link will always route to the current Active version of the standard. Although aetm of the requirements within ASTM A are relatively straightforward, other requirements related to surface preparation often require clarification. Inorganic binders are particularly suitable for paints applied in touch-up applications of undamaged hot-dip galvanized areas. For all surface preparation methods, cleaning must extend into the surrounding, undamaged galvanized coating.
Inspection of Cleaned Surfaces After surface preparation, the standards refer to points of inspection necessary to ensure proper adhesion of the repair material. The method and extent of surface preparation shall be mutually agreeable to the contracting parties. Always check for visible contaminants on the surface of the repair area just prior to mechanical cleaning. Topics include proper materials to use while performing the process, as well as specifications to follow and proper application of the repair materials.
When ready to perform mechanical cleaning, check the surface preparation standard for clarity on the allowable tooling methods.
Repairing HDG Steel
Hand tool cleaning with a stiff-bristle or nylon brush does not meet specification. There is no ASTM specification which specifies a maximum allowable repair size for galvanized items already accepted and delivered.
Historical Version s – view previous versions of standard. 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.
A listing of various manufacturers and products for the maintenance and repair of hot-dip galvanized structures is available for download. Inspector Listing – Non-U. Watch the Videos The main restriction in the specification for repairing newly galvanized material is the size of a70 area which is outlined in the product galvanizing specifications: Finally, a visual inspection to confirm the level of cleanliness must be carried out to astn the standard is met.
Touch-up materials asgm required to meet a coating thickness of at least 2. 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. ASTM A contains three acceptable methods of touch-up asym repair of hot-dip galvanized steel: