Electrochemical and spectroscopic investigation of synergistic effects in corrosion inhibition of aluminium bronze Part 2 – In acidified 4 wt-%NaCl solution

Abstract

Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy have been used to investigate changes of surface composition when 4-phenyl semicarbazide hydrochloride (PSC) is used as an inhibitor, with and without additions of KI, to suppress the corrosion of aluminium bronze in acidified 4 wt-%NaCl solution of pH 1.8 – 2 at 60 ° C. Anodic polarisation studies in the presence of the PSC inhibitor alone have shown oscillations of the corrosion current at elevated potentials owing to localised attack. The results of AES have shown that in the case of inhibition by PSC some depressions had formed on the surface, within which chloride species were present due either to localised attack by Cl- at weak points in the inhibitor film or to the adsorption of Cl- at the depressions, preventing the formation of a Cu – PSC protective film. In contrast, a synergistic effect between PSC and KI suppressed the occurrence of current oscillations and the development of surface depressions during anodic polarisation owing to the formation of a continuous CuI – PSC film, which can retard or stifle localised attack.