Title: Anodic oxidation of aluminium in sulphuric acid monitored by ex-situ and in-situ spectroscopic ellipsometry
Abstract: Abstract The growth of anodic oxide films on bulk aluminium in sulphuric acid (3 M H 2 SO 4 ) was monitored by means of ex-situ and in-situ spectroscopic ellipsometry in the photon energy range 1.5–5.0 eV. The ellipsometric results clearly reveal the growth of a porous film with increasing void fraction. The film thickness is directly proportional to the anodization time. Good agreement between experimental spectra and simulated data is obtained by assuming a two-layer model with an interface layer between the Al substrate and the porous aluminium oxide film. The addition of chloride to the electrolyte drastically reduces the film thickness for Cl − concentrations above 15 mmol. Open-circuit dissolution of the anodic oxide film grown in 3 M H 2 SO 4 proceeds within the pores and is not affected by Cl − in the electrolyte up to concentrations of 80 mmol. The optical properties of the Al substrate and the aluminium oxide are compared with data in the literature. Ex-situ and in-situ spectroscopic ellipsometry results for electrochemical oxide formation on Al are in good agreement, supporting the relevance of ex-situ measurements for this particular system.
Publication Year: 1993
Publication Date: 1993-10-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 11
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