Corrosion Inhibition of Pure Aluminium and Alloys AA2024-T3 and AA7075-T6 by Cerium(III) and Cerium(IV) Salts

The corrosion protection of pure aluminium and its alloys AA2024-T3 and AA7075-T6 has been studied in 0.1 M NaCl with and without the addition of Ce(III) chloride, Ce(III) nitrate, Ce(III) acetate and Ce(IV) sulfate. The study of Ce(III) acetate has been scarce but is here shown to be the most effective of the cerium salts studied, especially for AA7075-T6. The inhibition effectiveness of cerium salts is: Ce(III) acetate > Ce(III) chloride > Ce(III) nitrate for the metals studied. Ce(IV) sulfate does not inhibit corrosion. Electrochemical potentiodynamic measurements were used to investigate the mechanism of inhibition by cerium salts. Immersion tests in 0.1 M NaCl, with and without the addition of Ce(III) chloride and Ce(III) acetate, were performed to determine the effects of the inhibitors on the extent of corrosion damage at the surface of all three metals. For pure aluminium the inhibitory effectiveness was 78.5%, 82.6% and 84.0% in the presence of 3 mM Ce(III) nitrate, chloride and acetate, respectively. For AA7075-T6 the values of 92.1%, 99.1% and 99.6% were obtained. The inhibitory effectiveness of cerium salts is shown to depend on a variety of factors: type of substrate, type of anion and salt concentration.