abstract
The Volta potential difference (VPD) of oxide layers formed on an aluminum surface as a result of anodization in a neutral solution of boric acid, thermal oxidation in air, and immersion in boiling water was studied by scanning Kelvin probe force microscopy. The measured VPD value was correlated with the layer thickness. It has been suggested that the measured VPD value is contributed by induced potential from the charges trapped by defects. Provided that the defects created during oxidation and thereby the embedded charges are mainly concentrated at the film borders, the induced potential depends linearly on film thickness. The observed difference in the linear dependence of VPD on the thickness of anodic films has been explained in terms of their charge distribution profiles. The effect of annealing in air on the VPD of the anodic films has been associated with charge redistribution and partial disappearance of the defects. It was shown that, on annealing, the VPD of the anodic films tends to the equilibrium level which is the VPD value for a nonanodized film thermally oxidized at the given annealing temperature.
keywords
OXIDE FILM GROWTH; THERMAL-OXIDATION; ATOMIC-FORCE; CORROSION-INHIBITORS; FILIFORM CORROSION; IONIC DIFFUSION; METAL CRYSTALS; SURFACE; KINETICS; ALLOY
subject category
Chemistry; Science & Technology - Other Topics; Materials Science
authors
Yasakau, KA; Salak, AN; Zheludkevich, ML; Ferreira, MGS
our authors
Andrei Salak
Principal Researcher
Kiryl Yasakau
Assistant Researcher
Mário Guerreiro Silva Ferreira
Retired Professor
Mikhail Zheludkevich
Invited Principal Researcheracknowledgements
The authors thank Dr. M. D. Cunha Belo for useful discussion. The Portuguese Foundation for Science and Technology (FCT-Portugal, grant SFRH/BD/25469/2005 and FCT-project PTDC/CTM/72223/2006) is gratefully acknowledged for financial support.