Temperature dependence of the pitting potential of high purity aluminium in chloride containing solutions

Slow scan anodic polarization experiments were conducted on high purity (99.99%) aluminium exposed to chloride containing solutions at temperatures ranging from 1 to 70 °C. The total anodic charge passed prior to stable pitting shifts towards higher values with increasing chloride concentration and there is a transition point at 30 °C above which a significantly greater amount of charge is involved. For all chloride concentrations, the pitting potential decreases with temperature according to a linear relationship, and also shows a transition at approximately 30 °C, with a much steeper decrease observed for the higher temperatures. Possible explanations for these two effects are discussed.