Microstructural influence on corrosion behavior of MgZnGe alloy in NaCl solution

The corrosion behavior of a novel Mg0.5Zn0.2Ge alloy in as-cast and extruded conditions is investigated in 0.9 wt.% NaCl solution. Scanning kelvin probe force microscopy measurements and local electrolyte drop corrosion tests demonstrated that the matrix dissolved preferentially in corrosive solution due to the nobler Volta potential of the Mg2Ge phase. A combination of potentiodynamic polarization, electrochemical impedance spectroscopy, hydrogen evolution and weight loss tests illustrated and quantified the corrosion performance of Mg0.5Zn (Control) and Mg0.5Zn0.2Ge alloys. The results revealed that the corrosion resistance of the Mg0.5Zn alloy was improved by micro-alloying with germanium (Ge) due to decreased cathodic kinetics. Furthermore, the corrosion resistance of the Mg0.5Zn0.2Ge alloy was enhanced by hot extrusion. According to element mapping analysis of the cross section of the alloys after corrosion, the improved corrosion resistance of extruded Mg0.5Zn0.2Ge alloy could be attributed to the increased incorporation of Zn and Ge elements in the outer layer of the corrosion products film. (C) 2018 Elsevier B.V. All rights reserved.