This paper investigates the structure of the copper-enriched layer formed at the alloy/anodic film interface during anodizing of Al-2 wt.% Cu binary alloy using transmission electron microscopy. It was revealed that theta' phase was formed within the copper-enriched layer. For the copper-enriched layer formed on {10 0} aluminum planes, the interface between the aluminum matrix and the theta' phase within the copper-enriched layer is coherent. For the copper-enriched layer formed on {110} and {111} aluminum planes, the interfaces between the aluminum matrix and the theta' phase within the copper-enriched layer are semi-coherent or incoherent. The interfacial coherency influences the formation of oxygen gas bubbles within the resultant anodic films. (C) 2015 Published by Elsevier Ltd.