Lanthanide salts as corrosion inhibitors for AA5083. Mechanism and efficiency of corrosion inhibition

The inhibition effect of trivalent lanthanide (Ce3+, La3+) cations toward the localized corrosion of 5083 aluminum alloy in chloride-containing solutions was investigated in the present work. Electrochemical impedance spectroscopy was employed to estimate the inhibition efficiency of the lanthanide species under study. Scanning Kelvin probe force microscopy was used to provide deeper understanding of the corrosion and inhibition mechanisms at the micro level. The results of electrochemical tests demonstrate effective hindering of the localized corrosion attack due to precipitation of highly insoluble deposits on cathodic intermetallics. Trivalent lanthanum cations confer a more effective corrosion inhibition in comparison to that of Ce3+. Superior inhibition of La3+ resulted from the formation of very dense hydroxide domes while cerium-based precipitates have a porous granulated structure. (c) 2008 The Electrochemical Society.