Corrosion resistance study of UNS A93105 aluminum alloy in neutral chloride and acid chloride solution

Abstract

The corrosion resistance of UNS A93015 aluminum alloy (A93015) was studied in neutral chloride solution at specific chloride concentration and in 3.5% neutral chloride solution at specific sulphate concentration by potentiodynamic polarization technique, open circuit potential measurement (OCP) and optical microscopy characterization. The presence of sulphate ions in the neutral chloride solution significantly increased the corrosion rate of A93015 compared to the solutions with chloride ions. At 0.5% NaCl concentration, the lowest corrosion rate of 0.255 mm/y was obtained in the neutral chloride solution which corresponds to polarization resistance of 1121 Ω. The corrosion rate value increased to 0.295 mm/y at 3.5% NaCl with significant cathodic shift in corrosion potential. The presence of sulphate ion in the neutral chloride solution significantly increased the corrosion rate of A93015. At 0.00625M sulphate ion concentration the corrosion rate is 4.739 mm/y while at 0.1M concentration, the corrosion rate is 22.176. OCP curves of A93015 at 0.5% and 3.5% NaCl concentration transited anodically to -0.651 V and -0.703 V with relative thermodynamic stability. A93015 OCP plots from 3.5% NaCl solution at 0.00625 M and 0.1 M SO4 2- ion concentration shifted the OCP plots cathodically with absence of potential transients which signifies improved thermodynamic stability.