Effect of some surface treatments on kinetics of aluminium corrosion in NaCl solutions at various hydrostatic pressures

Abstract

The effect of various surface treatments (grinding, polishing, and pickling) and of prefilming (anodizing and passivation). On the susceptibility of aluminium to pitting in 0·5M NaCl solution at 20°C under various hydrostatic pressures has been studied. It was found that the susceptibility to pitting increased and that the passivity range (the difference between the corrosion potential and the pitting protection potential) of samples that have not been prefilmed decreased with increasing pressure. Ground and polished specimens are more likely to suffer from localized corrosion, particularly at high pressures. The pitting protection potential remains constant over the entire pressure range for ground and pickled specimens, on which the nucleation and growth of pits take place. Prefilming drastically reduced the susceptibility of aluminium to pitting at both low and high pressures. Passivated specimens showed a higher free corrosion potential than did anodized specimens (the immunity range of aluminium is larger), but a lower resistance to localized corrosion (the pitting potential decreases).