The Migration of Metal and Oxygen during Anodic Film Formation

Beta‐ray spectroscopy and radiotracer techniques have been used to study the transport of metal and oxygen during anodic oxidation. Both species are mobile during oxide film growth on Al, Nb, Ta, and W, but in Zr and Hf only oxygen transport is observed. Radiotracer measurements showed that the amount of metal dissolving in the electrolyte was usually less than 1% of the total oxidized, but that for Al it could be as high as 40%, depending on the current density and electrolyte used.