Investigation of anodic oxide formation on AA 7075 in citric acid

Citric acid is an environmentally friendly and non-toxic chemical which forms barrier-like oxide films on AA 7075 during anodization. The passive behavior and the kinetic of the film formation is investigated in macro- and microelectrochemical experiments. Galvanostatic formed anodic oxide films are investigated by FT-IRRAS and SEM. The oxide films formed are dense and free of pores and mainly consist of Al2O3. The formation of insoluble aluminum citrates is excluded at the chosen pH, but a small fraction of citrate in the oxide film is evident and explained by Zn and Cu complexes, respectively, incorporated in the aluminum oxide layer.