Corrosion behaviors for peak-aged Mg–7Gd–5Y–1Nd–0.5Zr alloys with oxide films

The corrosion behaviors of T5 (225 °C, 6.5 h) and T6 (460 °C, 2 h + 225 °C, 12 h) peak-aged Mg–7Gd–5Y–1Nd–0.5Zr alloys with oxide films were investigated by optical microscope (OM), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The weight loss rates and electrochemical tests were also analyzed. The thicknesses of T5 and T6 oxide films are roughly 0.6 and 1.0 μm, respectively. The components of oxide films mainly consist of O, Mg, Y, Nd, and Gd, and the T6 oxide film results in surfaces with larger peaks than T5 oxide film. In addition, Y, Nd, and Gd peaks are all higher than those of Mg–7Gd–5Y–1Nd–0.5Zr alloys, but Mg peak is consistently far below than that of the alloys. The specimens could be arranged in decreasing order of corrosion rates and corrosion current densities: T6 oxide film < T5 oxide film < T6 without oxide film < T5 without oxide film. The oxide films are compact to increase the corrosion resistance for Mg–7Gd–5Y–1Nd–0.5Zr alloys, which will provide a guiding insight into the corrosion and protection of Mg–RE alloys in atmospheric environments.