Different oxide structures can be formed on passive stainless steel sternal wires by various surface modifications. Oxide structure has a significant influence on the efficacy and biocompatibility of the medical devices. In this study, cathodic reduction was used to distinguish the oxide structures on 316L stainless steel sternal wires in a buffered phosphate electrolyte. TEM, Auger depth profile, XPS, and SEM were applied to examine the oxide structures. Interfacial resistance was measured using electrochemical impedance spectroscopy. Results indicate that cathodic reduction profiles have the capability to identify oxide structures on the passivated medical devices. (C) 2011 Elsevier B.V. All rights reserved.