Zinc chromate plating is a process that can add many beneficial properties to metal, particularly to protect it. There are different levels of protection provided by the coating that can sometimes be determined visually. Also to zinc, there are other applications for chromate coatings. There are different materials used for the coating process based on desired benefits and environmental concerns.
Why Plate Something in Zinc Chromate?
The basic reason for using zinc chromate plating is to make items more durable, particularly tools and small parts. The coating is soft when applied, but it will harden into a solid protective coating. Since the chromate coating cannot be applied directly to steel or iron, zinc is applied as a plating to give the material the properties of chromated zinc.
The plating works like paint to protect the piece from white corrosion. It also gives a coated piece a color that can be quite pleasing to the eye. If additional color is needed, the plating can act as a primer for a coat of paint.
Levels of Zinc Chromate Protection
While any zinc chromate plating offers some corrosion resistance, you can tell by the color approximately how much protection is provided. The colors range from clear/blue to black, with several colors in between, like yellow and olive drab. In general, darker coatings mean more corrosion resistance, but this method of evaluation is not foolproof. Sometimes dyes are added to the coating, so the color could be different from the level of protection.
Types of Chromate Coatings
Chromate conversion coatings can be applied to zinc, aluminum, copper, magnesium, tin, silver and cadmium alloys. Also to the aesthetic and durability reasons, for some of these metals, the coating is a way to retain electrical conductivity for the piece.
When it comes to chromate coatings, many are made from highly toxic hexavalent chromium, but they are being supplanted by the more environmentally friendly non-hexavalent chromium coatings like trivalent chromium.
The specific formulas used to create vary quite a bit, and they are often proprietary. The different compositions can create different desired effects in the finished coating. The exact processes used to create the coating are also sometimes proprietary.
Visit to learn more about chromate plating. Dekalb Metal Finishing has been providing metal finishing services for over 70 years, and they can provide the services you need. Visit www.dekalbmetal.com.