Uncovering Zinc Chromate Plating

Zinc chromate plating involves chromate conversion. Chromate conversion coating is a type of conversion coating used to passivate steel, aluminum, zinc, cadmium, copper, silver, magnesium and tin alloys. It is primarily used as a corrosion inhibitor, primer, decorative finish, or to retain electrical conductivity.

Who Invented Zinc Chromate?
Zinc chromate was developed by the Ford Motor Company in the late 1920s as a primer coating. Around 1936, zinc chromate was used by the aviation industry and the U.S. military. As zinc chromate is sensitive to light, it is mixed with black pigment to offer some UV protection.

What are the Properties of Zinc Chromate?
The molecular formula for Zinc chromate is ZnCrO4. Naturally, it appears as yellow-green crystals. Also, a wide range of pigments are supplemented at the time of manufacturing process to give it the color needed for the consumer. A most common color is rusty red, used on automobiles. Commonly, the aerospace industry uses yellows and greens. It is an odorless yellow solid powder. The melting point of Zinc chromate is 316 degree centigrade.

How is Zinc Chromate Produced?
A process known as the Cronak process is used to create zinc chromate for use in industry. This process is done by putting zinc or a zinc plated metal in a solution of sodium dichromate and sulfuric acid for a few seconds.

How Does Zinc Chromate Plating Work?
Zinc chromate is usually sprayed on in a paint booth, where it acts as a primer to defend zinc plated metal or aluminum alloys having zinc. It works by reacting with the surface of the metal when it gets damp. Once the moisture goes through it, the primer starts to dissolve and produces a shield, or passive layer, between the metal and the primer which protects from corrosion.

What are Some Uses for Zinc Chromate?
* The most common use of zinc chromate is as a corrosion inhibitor.
* Its application as a corrosion resistant agent was used in aluminum alloy parts initially in commercial aircraft and later in military aircrafts.
* Zinc chromate primer is commonly sprayed in paint booths to prevent corrosion.

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