Rare earth chloride and nitrate salts as individual and mixed inhibitors for aluminium alloy 7075-T6 in chloride solution

Abstract

The aim of the study was to investigate various rare earth salts as corrosion inhibitors of aluminium alloy 7075-T6. Rare earth salts, CeCl₃, LaCl₃, Ce(NO₃)₃ and La(NO₃)₃, were studied, first as individual inhibitors in the concentration range between 0.001 and 0.05 M. Second, the inhibitory effect of mixtures of chloride or nitrate salts was studied at an overall inhibitor concentration of 0.01 M. The corrosion properties of AA7075-T6 in the absence and presence of individual and mixed rare earth salts were investigated using electrochemical potentiodynamic technique in 0.1 M NaCl. The topography, morphology and composition of the inhibited surfaces were recorded. The highest inhibitory effectiveness was exhibited by CeCl₃, followed by mixtures of CeCl₃ and LaCl₃. During immersion for 12 h the corrosion protection remained high. Nitrate rare earth salts showed less protection, both as individual or as mixed inhibitors. Deposits containing both cerium and lanthanum were formed primarily on Cu-based intermetallics.

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