Advanced Surface Technologies Blog Chromate Conversion Coating for Aluminum

Chromate conversion coatings are the most widely used coating for corrosion protection of Aluminum Coatings and Corrosion Protection Chromate conversion coatings are used to passivate metals using an immersion bath process. The chromate conversion coating is a thin film that is applied by immersing the metal in a solution containing hexavalent chromium ions, which react with aluminum oxide on the surface of the metal to form a protective layer. This reaction forms a very stable complex with the chromium ion. The coating can be applied as either a single-stage or two-stage process. In the first stage, the metal is immersed in a dilute acid solution containing hexavalent chrome (Cr(VI)) ions, which reacts with the aluminum oxide to produce CrO3−2Al2O3. During this step, some of the hexavalent chromium is reduced to trivalent chromium (Cr(III)). After rinsing, the coated metal is then dipped into a second solution containing hexavalent and/or trivalent chromium Read more…