Electrogalvanization

Electrogalvanization is a metal coating process in which a thin layer of zinc is deposited on iron or steel by electroplating. The workpiece serves as the cathode in an electrolytic bath containing zinc salts, with zinc typically used as the anode. Substrate preparation includes degreasing, pickling, and thorough rinsing. Plating is performed at controlled temperatures and current densities to achieve the desired coating thickness, which typically ranges from about 5 to 25 micrometers (0.2 to 1 mil). Additives in the bath influence throwing power, brightness, and ductility.

The resulting zinc coating provides sacrificial corrosion protection: when the coating is damaged, zinc preferentially corrodes, protecting the underlying steel. Coatings can be bright, dull, or matte depending on bath composition and post-treatment. After plating, surfaces may be passivated with chromate or other conversion coatings to improve corrosion resistance and paint adhesion.

Applications include automotive parts, fasteners, appliance hardware, and various structural components, especially where complex geometries are required. Compared with hot-dip galvanizing, electrogalvanized coatings are thinner and more uniform, making them well suited to precision parts and assemblies with tight tolerances. However, they generally offer lower overall corrosion resistance in aggressive environments and can be damaged more readily by mechanical abrasion. Hydrogen embrittlement concerns may arise for high-strength steels if process controls are not observed.

Environmental and safety considerations include the use of zinc-based electrolytes, commonly zinc sulfate or zinc chloride with boric acid and additives; many cyanide-containing baths have been phased out. Waste treatment and acid handling are essential. Standards from ASTM and ISO govern zinc coatings, including electroplating specifications.