Vanadate post-treatments of anodised aluminium and AA 2024 T3 alloy for corrosion protection

Abstract

Porous anodic films formed on aluminium in sulphuric acid were post-treated using various double-dip processes that incorporate a sparingly-soluble, vanadate, corrosion inhibitor. The processes were optimised by investigating the effects of the double-dip order, the rinsing step, the immersion time and the double-dip method. The optimised processes were applied to AA 2024-T3 alloy, which was then exposed to salt spray. V-Ce(III) and V-Zn processes provided corrosion protection similar to that of sealed, sulphuric acid-formed films. A V-Ni process provided increased protection, similar to that of hot water sealed films formed in chromic acid.