Plasma electrolytic oxidation (PEO) coatings were fabricated on AA1060 commercial pure aluminum and detached from the substrate by an electrochemical method. The front view and fracture cross-section morphologies of the coating/substrate (C/S) interface were observed by scanning electron microscopy (SEM). The results show that the C/S interface layer consists of inter-connected tiny globular particles. During the PEO process, the thickness of the C/S interface layer and the diameter of the inter-connected tiny globular particles maintain approximately constant values of ~1μm and ~0.7μm, respectively. Based on the results, a C/S interface discharge mechanism is proposed and discussed.