Electroplating

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

The most common zinc electrolyte-anode arrangementuses lead-silver, or other insoluble anodes and electrolytesof zinc sulfates. Soluble anodes of pure zinc are also used.The coating develops as positively charged zinc ions inthe solution are electrically reduced to zinc metal anddeposited 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 applicationsto continuous sheet galvanizing or wire galvanizing.The most common applications are in automobile andappliance bodies and fasteners. Furthermore, to extendthe service life, electrogalvanized coatings can be treatedto 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 thicknessesup to 0.36 mils (9.1 μm) 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% reductionin area, depending on the chemical composition of the wire, heat treatment, and diameter.