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Johnson, Alan John (1964) The anodic behaviour of U, Ti, Zr, Nb and Ta in non-aqueous ethereal solutions. Doctoral thesis, Sir John Cass College.
The effect of pretreatment of U and Fe substrates prior to Al electrodeposition from AlCl3-LiAlH4-ether has been investigated. Deposits having good coverage and adhesion were readily obtained on steel specimens, after anodic etching in acid solution. Deposits obtained on U specimens, even after etching in acid to remove the oxide film, had poor adhesion and only moderate covering power. Anodic polarization of U specimens in the organic plating solution prior to Al deposition was found to improve the covering power of the deposit, although adhesion was not significantly increased. Poor adhesion of deposits was attributed to the presence of surface oxide films on the IT and a more detailed study has been made of the effects of anodic polarization in 3 M AlCl3-ether (the basis of the Al plating solution) on the removal of surface oxide films from U. Electrode potential measurements have been used throughout in an attempt to assess oxide removal. The results of anodic polarization studies on U were found difficult to interpret in the absence of data for the anodic behaviour of other metals in the 3 M AlCl3-ether. The investigation was therefore extended to include studies of the anodic polarization of other metals which readily form surface oxide films, i.e. Ti, Zr, Nb and Ta. It appears that the open-circuit electrode potentials for the metals studied may be best interpreted by considering them to form electrodes in which two reactions control the potential. Anodic polarization studies have shown that, in this solution, Ti and Zr may be micropolished, Nb and Ta selectively etched whilst U exhibits pitting attack. It is suggested that the anodic attack is dependent on the nature of metal chloride or mixed oxide-chloride films which may be present on these metals during anodic polarization. The general mechanisms proposed to explain the phenomena of passivity and micropolishing in aqueous solutions appear to be applicable in this solution.
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