Cyclic polarization behavior of aluminum oxide films in near neutral solutions

Cyclic polarization measurements have been made on abraded Al in near neutral borate, chromate, phosphate, and sulfate solutions. In both borate and chromate solutions, the currents continued to decrease with each subsequent cycle due to oxide thickening. In contrast, a significant rate of oxide dissolution occurred to produce reproducible repetitive curves during subsequent cycles in a phosphate and a sulfate solution. The current responses in a borate and a chromate solution were simulated using the high field conduction oxide growth model. The polarization behavior in a phosphate solution required inclusion of oxide dissolution in the model. The result in a sulfate solution was more complex, and was attributed to the interaction of sulfate ion at the oxide/solution interface. (C) 2001 The Electrochemical Society.