The relation between morphology and potential on localized dissolution of aluminum alloys

Abstract

To investigate pitting growth characteristics of aluminum alloys observations of dissolution morphology within the pits formed after immersion corrosion test in tap water were carried out, and they were discussed in comparison with the anodic dissolution morphology in AlCl₃ solution assuming localized corrosion environment. Dissolution morphology within the pits after immersion corrosion test could be well simulated with that after anodic dissolution in AlCl₃ solution. The morphology was closely related with the electrochemical properties of the alloys, such as the level of pitting potential. For example, in aluminum and the more noble alloys (100) type of crystallographic pits, while, in the less noble alloys less crystallographic dissolutions were observed, respectively. On the other hand, (100) type of crystallographic pits could be observed even in the less noble alloys after the dissolution in the sufficiently noble potentials. With these results it can be concluded that the difference of dissolution morphology of aluminum alloy is caused, not by the additional elements themselves, but by variation of dissolution potentials.