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Volume 121, 2002
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Visualization and characterization of electroactive defects in the native oxide film on aluminium

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Abstract

Spatially localized electrochemical activity at Al/Al2O3 electrodes has been investigated using scanning electrochemical microscopy (SECM) in order to establish the relationship between localized corrosion of Al (and Al alloys) with the defect structure of the native Al2O3 film. Local electron transfer at microscopic defects (2 to 50 μm radius) was visualized in acetonitrile solutions using the nitrobenzene/nitrobenzene radical anion (E° ∼ −1.6 V vs. Ag/Ag+) and tetracyanoquinodimethane/tetracyanoquinodimethane radical anion couples (E° ∼ −0.3 V) as redox mediators for imaging. SECM investigations revealed no significant differences in electrochemical activity at Al/Al2O3 electrodes in the two mediator solutions, indicating that electrical conduction at the defect sites is weakly dependent on interfacial potential and the electric field across the Al2O3 film. The density of electroactive defects observed by SECM varied by 2 to 3 orders of magnitude between electrodes prepared from the same source of Al (either 99.45% and 99.9995%) suggesting that electrical conduction in the native oxide is very sensitive to surface preparation. Defect densities as low as ∼3 sites cm−2 were readily measured by SECM.

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Publication details

The article was received on 11 Feb 2002, accepted on 12 Feb 2002 and first published on 26 Apr 2002


Article type: Paper
DOI: 10.1039/B201539K
Citation: Faraday Discuss., 2002,121, 199-210
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    Visualization and characterization of electroactive defects in the native oxide film on aluminium

    I. Serebrennikova, S. Lee and H. S. White, Faraday Discuss., 2002, 121, 199
    DOI: 10.1039/B201539K

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