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Tuesday, October 7, 2008: 4:00 PM
Carson City Room I (Flamingo Las Vegas)
Effect of Alloying Elements on the Growth of Anodic Film on Aluminium Alloys
X.Zhou, F. Roeth, M. Curioni, T.Hashimoto, G.E.Thompson and P.Skeldon,
Corrosion and Protection Centre, School of Materials, TheUniversity of Manchester , Manchester , M60 1QD, UK
Abstract
For commercial applications, alloying elements are added to aluminium in order to achieve the required mechanical properties. The alloys require surface treatment for effective performance under service conditions. In the present study, the effect of alloying elements on the growth of anodic film on aluminium alloys has been investigated.
It is revealed that alloying elements with Gibbs free energies of oxide formation per equivalent greater than that of alumina enrich at the alloy/film interface; when a critical enrichment is reached, oxidation of the alloying elements occurs. For copper-containing alloys, the structure of copper-enriched layer is grain orientation dependent. Consequently, such dependence has significant effect on the morphology and properties of the oxide film. It is also revealed that Mg, Li and Zn individually cause the anodic film to detach from the alloys during film growth. Detachment of the anodic film from the alloys is preceded by the formation of voids at the alloy/film interface. This phenomenon is a potential threat to the anodising of Mg or Li or Zn containing aluminium alloy since a good bonding of film to alloy surface is essential for a protective oxide film on an alloy.
X.Zhou, F. Roeth, M. Curioni, T.Hashimoto, G.E.Thompson and P.Skeldon,
Corrosion and Protection Centre, School of Materials, The
Abstract
For commercial applications, alloying elements are added to aluminium in order to achieve the required mechanical properties. The alloys require surface treatment for effective performance under service conditions. In the present study, the effect of alloying elements on the growth of anodic film on aluminium alloys has been investigated.
It is revealed that alloying elements with Gibbs free energies of oxide formation per equivalent greater than that of alumina enrich at the alloy/film interface; when a critical enrichment is reached, oxidation of the alloying elements occurs. For copper-containing alloys, the structure of copper-enriched layer is grain orientation dependent. Consequently, such dependence has significant effect on the morphology and properties of the oxide film. It is also revealed that Mg, Li and Zn individually cause the anodic film to detach from the alloys during film growth. Detachment of the anodic film from the alloys is preceded by the formation of voids at the alloy/film interface. This phenomenon is a potential threat to the anodising of Mg or Li or Zn containing aluminium alloy since a good bonding of film to alloy surface is essential for a protective oxide film on an alloy.