A contribution to the understanding of a.c. anodizing of aluminium

Commercial Al has been anodized in 10% v/v sulphuric acid using AC. At 20 V no significant differences in colour and thickness between specimens anodized at the neutral and live terminals were detected. At higher voltages the oxide on the neutral specimens was always more yellow and thinner than tha...

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Bibliographic Details
Published in:Journal of applied electrochemistry 1989-11, Vol.19 (6), p.829-838
Main Authors: BARBOSA, M. A, GABE, D. R, ROSS, D. H, SUTHERLAND, I
Format: Article
Language:English
Subjects:
Applied sciences
Corrosion
Corrosion mechanisms
Cross-disciplinary physics: materials science
rheology
Exact sciences and technology
Materials science
Metals, semimetals and alloys
Metals. Metallurgy
Physics
Specific materials
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Summary:Commercial Al has been anodized in 10% v/v sulphuric acid using AC. At 20 V no significant differences in colour and thickness between specimens anodized at the neutral and live terminals were detected. At higher voltages the oxide on the neutral specimens was always more yellow and thinner than that on the live specimens. The colouration was attributed to the reduction of sulphate to sulphide during the cathodic half-cycle, no other sulphur-containing species being detected by XPS. EPMA has shown that the total S distribution across the film was practically uniform and independent of the operating conditions, except in thin films, where it was greatest at the free surface. With additions of ferric sulphate to the solution, the reduction to sulphide was inhibited and the differences between live and neutral specimens were avoided. The total amount of S remained unchanged at approx 5 wt% and no Fe was incorporated in the film. Graphs, spectra, photomicrographs. 16 ref.--AA
ISSN:0021-891X
1572-8838
DOI:10.1007/BF01007930