Corrosion Behavior of Ultra Fine Grain Pure Magnesium for Automotive Applications

The contemporary challenge in automotive industry is weight reduction. Compared to conventional automotive materials, commercially pure magnesium is having enhanced strength-to-mass ratio and low density, which confers to optimal requirement for automotive applications. Amongst various other reasons such as low hardness, low corrosion resistance also prevents it from entering mass production. Severe plastic deformation by equal channel angular extrusion (ECAE) is regarded as one of the prominent methods to increase the mechanical properties of magnesium. However, the investigation in corrosion resistance of extruded magnesium in automotive environment is not discussed in depth. This paper discusses the microstructure and corrosion characteristics of commercially pure magnesium which has been extruded by ECAE at 473 k through the routes a and b_c up to eight passes and their three surfaces (extrusion direction, normal direction & transverse direction) in detail. The corrosion experiment has been performed using conventional electrochemical techniques such as open-circuit potential measurements and potentiodynamic polarization method in 3.5 wt% NaCl solution environment. The surface morphology of the magnesium billet was examined in detail using scanning electron microscopy (SEM) and the hardness was measured using micro Vickers hardness tester.