Zinc-Chromate-Plating Properties

Zinc chromate is a commonly used pigment. The addition of chromate during the plating process gives producers the ability to enhance metals with different colors. Consequently, zinc-chromate plating is becoming a commonly employed decorative coating. Some of your home's accents may feature zinc-chromate plating.

Corrosion Inhibitor

• Electrodeposited zinc protects steel from exposure to corrosion. The addition of a chromate gives manufacturers an opportunity to vary how much corrosion resistance the metal will have, according to Rick Holland, technical manager of Columbia Chemical Corporation. Zinc plating is effective because "zinc sacrifices itself and thus corrodes before the base metal."

Colors

• The natural color of zinc chromate is yellow, but the standard color of zinc-chromate plating, according to Platers and Anodizers Online, is blue-bright or clear--a chromelike color that provides the least corrosion protection. Yellow chromate gives better corrosion resistance and costs less. The corrosion resistance of black chromate can vary from poor to outstanding, Platers and Anodizers Online says. Olive drab (army green) chromate offers an outstanding corrosion resistance.

Thickness

• Before the addition of chromate, the thickness of zinc plating ranges from 0.00015 to 0.001 inches thick. A thickness of 0.0002 is a common standard. But a 0.0005-inch coating provides a superior amount of corrosion protection.

Cyanide Content

• Unless you are sure the item emerged from a noncyanide bath, treat these plated items with care. Despite a worldwide push away from cyanide zinc, cyanide baths may still be used for zinc-chromate plating. Therefore, standard precautions are necessary with materials that have zinc-chromate plating.