The effects of the electrochemical anodization of deoxidized 2024-T3 aluminum on copper were characterized by Auger electron spectroscopy and Rutherford backscattering. Anodization was performed in phosphoric acid at a constant potential. Data are presented which show that constant potential anodization of 2024-T3 is more efficient than that of aluminum in terms of oxide growth rates for short anodization times. However, the maximum anodic thickness achievable on the alloy is less than that achievable on the pure metal. Copper is shown to be enriched at the oxide-metal interface because of its diffusion from the bulk during anodization. Possible effects of copper on oxide growth mechanisms and oxide morphology are discussed.