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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Ensure a blotter test is performed prior to using a compressed air source in accordance with ASTM D Touch-up materials are required to meet a coating thickness of at least 2. 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.

ASTM AZinc Dust in Paint | American Galvanizer’s Association

The area being repaired needs to be preheated to approximately F C. Correct for the additional tape thickness i. The repair coating thickness must meet the specification requirement for the material category of the part with a maximum thickness of 4 mils ?

The zinc used is nominally Effective May 1st Most organic zinc-rich paints are not critical of climatic or atmospheric conditions for curing. There aastm no ASTM specification which specifies a maximum allowable repair size for galvanized items already accepted and delivered.

ASTM A780-Zinc Dust in Paint

Touch-up and repair of galvanized steel is simple whether newly galvanized or in service for years. Finally, a visual inspection to confirm s780 level of cleanliness must be carried out to ensure the standard is met.

It is important to note that the size restrictions apply to the area s to be repaired prior to surface preparation. 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. Always check for visible contaminants on the surface of the repair area just prior to mechanical asfm.

The damage may be the result of welding or cutting flamein asmt case the coating will be damaged predominantly by burning.


The method and extent of surface preparation shall be mutually agreeable to the contracting parties. Topics include proper materials to use while performing the process, as well as specifications to follow and proper application of the repair materials.

However, do not clean excessively beyond the area of repair. This practice can also be used to repair hot-dip galvanized coatings damaged by excessively rough handling during shipping or erection.

A listing of various manufacturers and products for the maintenance and repair of hot-dip galvanized structures is available for download. This abstract is a brief summary of the referenced standard.

Where circumstances do not allow blast cleaning, it is permissible to power disk sand areas to be repaired to bright metal. Galv Touch Up Methods Dr. For power tool cleaned surfaces, a surface profile depth micrometer is the appropriate atm for confirming profile, unless otherwise agreed.

ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date. Inspector Listing – Non-U. 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 ast, the galvanizing facility.

ASTM A contains three acceptable methods of touch-up and repair of hot-dip galvanized steel: 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: Within the a70 of asttm specification and where appropriate, SI units are shown in brackets.

Paints containing zinc dust are classified as organic or inorganic, depending on the binder they contain. Therefore, once in-field, any size of repairable coating defect can be touched up.

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. Zinc-based solder products closely match the surrounding zinc and blend in well with the existing coating appearance.


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. 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 specification explains how to use the various repair methods as well as the required coating thickness for the repaired area. Each system shall be used independently of the other without combining values in any way. For all surface preparation methods, cleaning must extend into the surrounding, undamaged galvanized coating.

Surface Preparation Always check for visible contaminants on the surface of the repair area just prior to mechanical cleaning. Surface profiling for abrasive blast cleaned a7800 may be performed using any method listed within ASTM D visual comparator, surface profile depth micrometer, or replica tape. Galv Touch-Up and Repair Dr. Contact Us Order Status. Topics will include proper equipment and materials to use while performing the process, explanation aa780 the specifications to follow, and examples of best practice during application of the repair materials.

Repairing HDG Steel

Soldering is done with zinc-based alloys in either a stick or powder form. This is especially applicable for abrasive blast cleaned surfaces, where an appropriately sized blasting unit and hose should be utilized. For best results, thickness measurements for the metallized coating should be taken with either a magnetic or an electromagnetic gauge.

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. Experience shows that in general organic zinc-rich systems are more tolerant of surface asm.

The information provided herein is not intended as a representation or warranty on the part of the AGA.