Abstract

RENTERIA RINCON, Isaías Andrés; GARCIA VERGARA, Sandra Judith  and  SKELDON, Peter. An impedance spectroscopy study of the anodically formed films on aluminium in cromic acid. Rev. ion [online]. 2012, vol.25, n.spe, pp.45-51. ISSN 0120-100X.

The effect of current density on the mechanism of formation of porous anodic films on aluminum is investigated by impedance spectroscopy. The study employs porous anodic films formed in 0.25M chromic acid solution at 40°C. Selected samples were analyzed by scanning electron microscopy (SEM) and optical microscopy. The anodic films are composed for a thin barrier layer of constant thickness close to the metal/oxide interphase and an external porous layer of several microns at oxide/electrolyte interphase. The increase in current density affects the morphology of the anodic films. At lower current densities feathered porous structure were developed. Meanwhile at high current densities a thick barrier layer is formed. The formation of porous layers is the result of the dynamic process of growth and dissolution of anodic alumina at the pore base.

Keywords : aluminium; anodizing; anodic films; chromic acid.

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