Corrosion resistance study of UNS A96110 aluminum alloy in chloride-sulphate solution

Abstract

Electrochemical analysis of the corrosion resistance of UNS A96110 aluminum alloy (UN6110) in neutral chloride media at 0.5%, 1%, 1.5%, 2%, 2.5%, 3% and 3.5% NaCl concentration, and 3.5% NaCl/sulphuric acid solution at concentrations of 0.00625 M and 0.1 M by potentiodynamic polarization method. UN6110 exhibited lower corrosion in the acid chloride solution compared to the results obtained from the neutral chloride media. The lowest corrosion rate (0.097 mm/y) was obtained from the neutral chloride solution at 0.5% NaCl corresponding to corrosion current density of 8.78 x 10-6 A/cm2 and polarization resistance of 2927 Ω while the highest value 0.344 mm/y was obtained at 3.5% NaCl concentration. Polarization plot showed significant variation at the anodic portion of the polarization plots with visible potential transients on the passivation portion of the plot. The aluminium alloy exhibited passivation reaction mechanisms due to formation and breakdown of the inert protective oxide. Variation of the cathodic polarization plots shows activation controlled reduction reactions. In sulphate-chloride solution, corrosion rate UN6110 significantly increased to 15.855 mm/y at 0.00625 M and 20.017 mm/y 0.1 M. Optical images obtained from the neutral chloride solution showed the presence of large micro corrosion pits and grooves due to the electrochemical action of chlorides. This differs from the images obtain from the acid chloride solution which showed general surface deterioration couple with well-defined micro and macro corrosion pits.