Trivalent Chromium Conversion Coating for Corrosion Protection of Aluminum Surface

Corrosion is the degradation or deterioration of metal components due to a reaction with the environment. Chromate conversion coating is applied to passivate metallic surface to slow down (and prevent to some extent) corrosion process. Chromate conversion process uses chromium compounds including hexavalent chromium, which is toxic, carcinogenic and hazardous to human health and environment. Hexavalent chromium is prohibited with mandates and regulations including various directives from European Union. Industry has developed trivalent chromium chemistries for chromate conversion coating. Trivalent chromium is more environmentally friendly and could be equally effective as hexavalent chromate. This paper will describe a newly developed trivalent chromium process for chromate conversion on aluminum, which has proven to be very effective with outstanding performance and has been used widely in aerospace industry. This process is certified to military QPL (Qualified Product Listing) standards. The same process is also used as anodic seal on anodized aluminum.