Corrosion protection provided by trivalent chromium process conversion coatings on aluminum alloys

This dissertation focuses on a fundamental understanding of the formation mechanism, chemical structure, and basic electrochemical properties of the TCP coating on three high strength aluminum alloys: AA2024-T3, AA6061-T6, and AA7075-T6. The formation of the TCP coating is driven by an increase in the interfacial pH. The coating is about 50-100 nm thick and has a biphasic structure consisting of a ZrO 2 /Cr(OH)3 top layer and an AlF63- /Al(OH)3 interfacial layer. The coating contains hydrated channels and or defects. -- Abstract.