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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Touch-up materials are required to meet a coating thickness of at least 2. Although the hot-dip galvanized coating is very resistant to damage, small voids or defects in the coating can occur during axtm galvanizing process or due to improper handling of the steel after galvanizing. Ensure a blotter test is performed prior to using a compressed air source in accordance with ASTM D When it comes to repairing galvanized steel in the field, there is no limitation to the size that can be repaired.
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:.
Inspector Listing – Non-U. To ensure that a smooth reconditioned coating can be effected, surface preparation shall extend into the undamaged galvanized coating. Within the text of this specification and where appropriate, SI units are shown in brackets.
Zinc-Rich Paints Zinc-rich paint is applied to a clean, dry steel surface by either a brush or spray. Although some of the requirements within ASTM A are relatively straightforward, other requirements related to surface preparation often require clarification. Brite Zinc meets and exceeds this percent.
Soldering is done with zinc-based alloys in either a stick or powder form. If replica tape is utilized, two readings are to be taken over each location and averaged to get one “measurement” of asttm profile of the surface. Galv What does the cold galvanizing process consist of?
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. Galv Touch-Up and Repair Dr.
Paints containing zinc dust are classified as organic or inorganic, depending on the binder they contain. This is especially applicable for abrasive blast cleaned surfaces, where an appropriately sized blasting ast, and hose should ashm utilized.
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. The zinc coating is difficult to atm, and field fabrication that requires removal of the coating should be minimized as much as possible. Historical Version s – awtm previous versions of standard.
Hand tool cleaning with a stiff-bristle or nylon brush does not meet specification. 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.
Any dust or loose residue from cleaning must be brushed away using a stiff-bristle brush or blown off using clean, dry air. Anyone making use of this information assumes all liability arising from such use. Appropriate grinding tools include reciprocating sanders, orbital sanders, or grinding devices that utilize abrasive cloths, discs, wheels or flaps.
Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard. The zinc used is nominally 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.
There is no ASTM specification which specifies a maximum allowable repair size for galvanized items already accepted and delivered. 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.
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.
Inspection of Cleaned Surfaces After surface preparation, the standards refer to points of inspection necessary to ensure proper adhesion of the repair material.
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. Topics include proper materials to use while performing the process, as well as specifications to follow and proper application of the repair materials. 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.
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.
Galv Touch Up Methods Dr. This material provides general information only and is not intended as a substitute for competent professional examination and verification as to suitability and applicability.
Experience shows that in general organic zinc-rich systems are more tolerant of surface preparation.