Oxidation properties of Mg-Y-Sn, Mg-Y and Mg-Sn alloys at 500 degrees C and corrosion behavior of the oxidized alloys were investigated. The results showed that Mg-Y-Sn and Mg-Y alloys exhibit better oxidation resistance compared with pure Mg and AZ31. Y-enriched oxide films were formed on the surfaces of Mg-Y-Sn and Mg-Y alloys after being oxidized at 500 degrees C for 6 h and the films are mainly composed of Y2O3 and MgO according to X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. The compact surface oxide film can effectively protect the matrix from oxidizing. Simultaneously, the electrochemical corrosion and immersion tests showed that corrosion resistance of the oxidized Mg-Y-Sn and Mg-Y alloys has been enhanced compared with the initial unoxidized alloys. Y plays a decisive role in improving the protective property of the oxide film. (C) 2015 Elsevier B.V. All rights reserved.