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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Authored by Alana Hochstein. In order to 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.
Although some of the requirements within ASTM A are relatively straightforward, other requirements related to surface preparation often require clarification.
The six-part video series will provide highly beneficial visual aids to those needing assistance with meeting the requirements of ASTM A Topics will include proper equipment and materials to use while performing the process, explanation of the specifications to follow, and examples of best practice during application of the repair materials.
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. At the galvanizing facility, the maximum allowable repair size for iron and steel products per ASTM A is no more than 1 inch [2.
Repairing HDG Steel | American Galvanizer’s Association
It is important to note that the size restrictions apply to the area s to be repaired prior to surface preparation. There is no ASTM specification which specifies a maximum allowable repair size for galvanized items already accepted and delivered. Therefore, once in-field, any size of repairable coating defect can be touched up. Always check for visible contaminants on the surface qstm the repair area just prior to mechanical cleaning.
Where such contaminants are found, the surface preparation standards associated with all repair materials require the removal of visible dirt, oil and grease deposits using a solvent cleaning method such as SSPC-SP1 Solvent Cleaning.
Repairing HDG Steel
When ready to perform mechanical cleaning, check the surface preparation standard for clarity on the allowable tooling methods. Appropriate grinding tools include reciprocating sanders, orbital sanders, or grinding devices that utilize abrasive cloths, discs, wheels or flaps.
Where blast or power tool cleaning cannot be performed, hand tool cleaning per SSPC-SP2 Hand Tool Cleaning allows the use of wire brushing, scraping, chipping and sanding. Hand tool cleaning with a stiff-bristle or nylon brush does not meet specification. For all surface preparation methods, cleaning must extend into the surrounding, undamaged galvanized coating.
However, do not clean excessively beyond the area of repair. This is especially applicable for abrasive blast cleaned surfaces, where an appropriately sized blasting unit and hose should be utilized.
After surface preparation, the standards refer to points of inspection necessary to ensure proper adhesion of the repair material. Do not immediately apply repair materials over a freshly cleaned surface. Any dust or loose residue from cleaning must be brushed away using a stiff-bristle brush or blown off using clean, dry air. Ensure a blotter test is performed prior to using q780 compressed air source in accordance with ASTM D For power tool cleaned surfaces, a surface profile depth micrometer is the appropriate method for confirming ast, unless otherwise agreed.
Surface profiling for abrasive blast cleaned surfaces may be performed using any method listed within ASTM D visual comparator, surface profile depth micrometer, or replica tape.
Do not average the x780, as this requirement was removed from the specifications in If replica tape is utilized, two readings are to be taken over each location and averaged to get one “measurement” of the profile of the surface.
Correct for the additional tape thickness i. Finally, a visual inspection to confirm the level of cleanliness must be carried out to ensure the standard is met. The material provided herein has been developed to provide accurate and authoritative information about after-fabrication hot-dip galvanized steel.
This material provides general information only and is not intended as a substitute for competent professional examination and verification as to suitability and applicability. The information provided herein is not intended as a representation or warranty on the part of the AGA. Anyone making use qstm this information assumes all liability arising from such use.
August 1, Authored by Alana Hochstein.
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.
Surface Preparation Always check for visible contaminants on the surface of the repair area just prior to q780 cleaning.
Inspection of Cleaned Surfaces After surface preparation, the standards refer to points of inspection necessary to ensure proper adhesion of the repair material.