Electrogalvanized (electroplated) coatings are created by applying zinc to steel sheets and strips by electro-deposition. Similar to sheet galvanizing, the operation is continuous and coating thickness is minimal. Applied in a steel mill, sheets or strips are fed through entry equipment into a series of washes and rinses, then into the zinc plating bath.

The most common zinc electrolyte-anode arrangement uses lead-silver or other insoluble anodes and electrolytes of zinc sulfates. Soluble anodes of pure zinc are also used. The coating develops as positively charged zinc ions in the solution are electrically reduced to zinc metal and deposited on the positively charged cathode (sheet steel). Grain refiners may be added to help produce a smooth, tight-knit zinc coating on the steel.

Electrogalvanized coatings are applied to sheet steels and wire; and therefore, are used in similar applications to continuous sheet galvanizing or wire galvanizing. The most common applications are in automobiles, appliance bodies, and fasteners. Furthermore, to extend the service life, electrogalvanized coatings can be treated to make them suitable for painting, and this is often recommended due to the extremely thin zinc coating.

Coating Characteristics

This electro-deposited zinc coating consists of pure zinc tightly adherent to the steel. The coating is highly ductile remaining intact even after severe deformation. Produced on strip and sheet materials, the coating weight ranges up to 0.2 oz/ft² (60 g/m²), or thicknesses up to 0.36 mils (9.1 ?m) per side, while on wire, coating weights may reach up to 3 oz/ft² (915 g/m²). The coating of pure zinc is thinner than continuous sheet galvanizing, mechanically-bonded, and there are no alloy layers, but provides a smoother finish. Heat-treated and electro-coated wire can be cold drawn to about 95% reduction in area, depending on the chemical composition of the wire, heat treatment, and diameter.