Chemical potential from extrinsic ions in oxide films on aluminum

摘要

X-ray studies of Cr in Al oxide films have shown that 3- and 6-valent Cr may be present. 300 nm Al films were anodized, cathodized or exposed to K(sub 3)Cr(CN)(sub 6), NaMoO(sub 4), KMnO(sub 4), or NaVO(sub 3) solutions. Cathodized surfaces were then anodized in borate solution. X-ray absorption at glancing angle and fluorescence detection were used to study species incorporated in the oxide surface. The 3-valent Cr present was closely related to Cr(OH)(sub 3). Absence of a pre-edge peak associated with the 6-valent Cr shows that conditions at the oxide surface did not produce chromates. Cr(CN)(sub 6)(sup 3(minus)) complex is not strongly absorbed on the surface, in contrast to chromates. The permanganate and vanadate solutions gave only 4-valent Mn and 5-valent V. The effective oxidation potential inside the oxide film is estimated. 11 refs., 2 figs., 2 tabs. (DLC)