Corrosion properties of glassy Mg70Al15Ga15 in 0.1 M NaCl solution

The corrosion behavior of glassy Mg70Al15Ga15 was investigated in 0.1 M NaCl solutions of various pH values. Potentiodynamic polarization measurements confirm a pronounced passivity for 4 ≤ pH ≤ 12. Corrosion currents in neutral solutions are found to be as low as 10−6 A/cm2. Optical microscopy and Auger electron spectroscopy were performed on samples immersed under open-circuit conditions in neutral, acidic and alkaline 0.1 M NaCl solutions to observe their time-dependent passive film formation. A significant incorporation of aluminum in the surface layers was found. The alloys show an unusual stability against dissolution in chloride-containing solutions, raising expectations of a highly corrosion-resistant Mg-based alloy. The time-dependent limitations of this stability are discussed in context with the surface films observed.