Steel and iron often earn their rust-resistance through galvanization, which involves coating the material in zinc. There are several alternatives for carrying this out, but hot-dip galvanizing (HDG)—the process of dipping steel into a kettle or vat containing molten zinc—is advantageous due to its inherent simplicity. However, regardless of its relatively basic procedure and resulting superior corrosion protection, due to the metallurgical reaction between the iron and molten zinc to form a tightly bonded alloy coating, hot-dip galvanizing benefits from the harmonized guidelines laid out in ASTM A123.
ASTM A123-17: Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products covers guidelines for zinc coating (galvanizing) by the hot-dip process on iron and steel products made from rolled, pressed, and forged shapes, castings, plates, bars, and ships.
ASTM A123-17 is applicable to both unfabricated and fabricated products, such as assembled steel products, structural steel fabrications, large tubes already bent or welded before galvanizing, and wire work fabricated from uncoated steel wire. It also covers steel forgings and iron castings too large to be centrifuged, but it does not, however, apply to wire, pipe, tube, or steel sheet that is galvanized on specialized or continuous lines. It is also not to be used for steel less than 22 gage thick.
The ASTM A123-17 document details specifications for materials, including the steel or iron, zinc, and bath composition, and coating properties, such as the coating thickness, finish, and appearance. In addition, it addresses sampling and test methods to assure that the zinc coating is being furnished properly.
ASTM A123-17 revises and replaces ASTM A123/A123M-15. Key alterations to the new edition include updates to the finishing specifications, the replacement of Figure 4 on “Uncoated Area Subject to Renovation,” and the change that continuous galvanizing of reinforcing bars is now to be in accordance with ASTM A1094/A1094M.
This specification is applicable to orders in either inch-pound units (as A123) or SI units (as A123M).
ASTM A123/A123M-17: Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products is available on the ANSI Webstore.