The corrosion behaviors of Mg–7Gd–5Y–1Nd–0.5Zr alloy under (NH4)2SO4, NaCl and Ca(NO3)2 salts spray condition

The corrosion behaviors of Mg–7Gd–5Y–1Nd–0.5Zr alloys after T5 treatment under (NH4)2SO4, NaCl and Ca(NO3)2 salt spray condition were investigated by weight loss rates, residual mechanical properties, scanning electron microscope (SEM), X-ray Diffraction (XRD) and potentiodynamic polarization tests. The corrosion degree of Mg–7Gd–5Y–1Nd–0.5Zr alloys in Ca(NO3)2 salt spray was very shallow by corrosion morphology and the corrosion route was extended along the surface in texture-like shape, while the alloy in NaCl and (NH4)2SO4 salt spray were major local corrosion and there were serious corrosion pits on the surface. The weight loss rates in (NH4)2SO4, NaCl and Ca(NO3)2 salt spray was respectively 0.4147, 0.1618 and 0.0725 mg/(cm2 d−1). The results of residual mechanical properties indicated that the corrosion order in salts spray of Mg–7Gd–5Y–1Nd–0.5Zr alloys is NH4SO4 > NaCl > Ca(NO3)2, which was consistent with the results of potentiodynamic polarization tests. The type of the salts will play a vital role in the initiation of the corrosion of EW75 alloy when they are used in the atmosphere environments. Inorganic salts with the smaller PH value after dissolution will have a stronger impact on the corrosion of EW75 magnesium alloys.