Improved corrosion resistance of Mg-8Sn-1Zn-1Al alloy subjected to low-temperature indirect extrusion

We report that the corrosion resistance of Mg-8Sn-1Zn-1Al alloy is significantly improved by the application of a low-temperature indirect extrusion process utilizing artificial cooling. It was found that the corrosion rates, measured by immersion tests in 0.6 M NaCl solution at 25 degrees C, are 27.5 and 246.7 mm y(-1) for the alloys extruded with and without artificial cooling, respectively. The remarkably improved corrosion resistance is mainly attributed to the reduced nobility of cathodic Al5Fe2 particles, which results in retarded microgalvanic corrosion in the corrosive condition. Metallurgical factors affecting the electrochemical nobility of Al5Fe2 particles are discussed