Effect of alloying elements on the growth of anodic film on aluminium alloys

In the present study, the anodic film growth on binary Al-3 wt.% Li, Al-2 wt.% Zn, Al-3 wt.% Mg and Al-2 wt.% Cu alloys is investigated. It is 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. For binary Al-2 wt.% Cu alloy and commercial AA2024 T351 aluminium alloy, the consequences of the enrichment of copper, the presence of copper species and oxygen in the film, and disruption of oxygen gas bubbles have significant effect on the morphology of both barrier and porous type anodic films. © 2009 by NACE International.