Cationic-Film-Forming Inhibitors for the Protection of the AA 7075 Aluminum Alloy Against Corrosion in Aqueous Chloride Solution

The corrosion rate of AA 7075 aluminum alloy in 0.1 M sodium chloride solution is decreased by the addition of 1000 ppm of FeCl2, CoCl2, NiCl2, YCl3, LaCl3, NdCl3, PrCl3, or CeCl3. In each case, the protective cation is slowly incorporated into the oxide film which develops on the alloy surface during exposure to the solution. The most protective of the cation additions examined (i.e., Ce3+, La3+, Pr3+, Nd3+, and Ni3+) developed surface films which modified the susceptibility to corrosion by suppressing the kinetics of the oxygen reduction reaction at cathodic sites on the surface.