Hot-dip galvanizing is one of the most economical, maintenance-free corrosion protection systems available. Like any other manufacturing process, hot-dip galvanized steel requires an inspection of the finished product to ensure compliance with applic...
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Hot-Dip Galvanized Coating Appearance
HDG steel may have a variety of different initial appearances, including bright and shiny, dull, spangled, mottled, or matte gray. This difference in initial appearance can occur between individual pieces and even between sections of the same piece. The initial appearance of hot-dip galvanized steel is hard to predict for a variety of reasons, including steel chemistry, cooling rate, and stress induced during steel processing.
Regardless of the initial appearance, all galvanized steel parts will take on a uniform matte gray appearance upon exposure to the environment, typically within six months to two years. As the coating is exposed to natural wet/dry cycles, it develops a protective zinc patina; the result is a soft gray appearance - evening out any differences in appearance that may have existed originally. Because superior corrosion protection depends on the thickness of the zinc coating rather than visual appearance, all coating appearances are acceptable upon inspection as long as they meet thickness requirements and don’t interfere with the intended use. No matter the visual appearance of the product, the steel will still benefit from the superior corrosion protection provided by hot-dip galvanizing. This publication describes initial appearance differences that may occur for a variety of reasons.