A novel acoustic method has been used to characterize the zeta potential and potential of zero charge in the pores of sulfuric acid anodized aluminum as a function of pH and concentration of oxo‐chromium(VI) compounds (those containing anions of chromate and dichromate). The results show that aqueous solutions of oxo‐chromium(VI) at a concentration of 0.01 M substantially lower the zeta potential of the internal surface of aluminum oxide pores without irreversibly adsorbing as the Cr(III) oxide. It remains as the adsorbed but otherwise soluble oxo‐Cr(VI) moiety. This explains in part the corrosion inhibition of anodized aluminum by oxo‐Cr(VI) compounds, since such a change in zeta potential discourages adsorption by .
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Kendig et al. (1999) studied this question.