Inhibition of Corrosion on AA2024-T3 by New Environmentally Friendly Rare Earth Organophosphate Compounds

Abstract The combination of rare earth metals (REM), such as Ce, La, Pr, or the less-refined mischmetal (consisting of a combination of REM) with dibutyl phosphate or diphenyl phosphate, provides a complex that shows excellent corrosion inhibition for AA2024-T3 (UNS A92024) in aqueous chloride environments. In some instances, it is equal to the inhibition provided by the chromate compounds, which are still used by the aircraft industry. The addition of these compounds as an inhibiting pigment in an epoxy coating also shows efficient suppression of filiform corrosion from scribes in the coating, under both alternate immersion and high-humidity conditions. Surface characterization of AA2024-T3 specimens immersed in solutions of these complex salts suggests that a film containing both the organic and rare earth components deposits on the alloy surface. The electrochemical data indicate that this film is acting as a mixed inhibitor, suppressing both the anodic and cathodic processes on the surface.