Relationship Between Al[sub 2]O[sub 3] Film Dissolution Rate and the Pitting Potential of Aluminum in NaCl Solution

Abstract

The dissolution rate of the film, (mol/cm2 s), and the pitting potential, of polycrystalline Al electrodes were measured in 50 mM mM solutions (pH 6.7) containing between 0 and 200 mM NaCl. was determined by analysis of the transient current, using the high-field growth model, following a large amplitude potential step to induce film growth in competition with film dissolution. The dissolution rate of the oxide film increased from mol/cm2 s in the absence of to a quasi-limiting value of mol/cm2 s at concentrations above ∼100 mM. Over the same concentration range, shifted to more negative potentials with increasing concentration, also approaching a quasi-limiting value of ∼−0.95 V vs. mercury/mercuric sulfate (saturated at concentrations greater than ∼100 mM. The similar functional dependencies of and on concentration suggest a strong correlation between oxide film dissolution and oxide breakdown. © 2004 The Electrochemical Society. All rights reserved.