Corrosion Behavior of Mg-Zn-RE Alloys (RE = Gd, Y, Nd)

The effect of different rare earth elements (Gd, Y, Nd) with similar atomic percentage on the corrosion behavior of Mg-1.52Zn (at.%) was investigated. The secondary phases and corrosion film formed on the surface of the alloys during immersion in aqueous NaCl solution affects the corrosion behavior of the alloy. The electrochemical, weight loss and hydrogen evolution tests revealed that corrosion rate of Mg-1.52Zn-0.15Gd was the highest and the corrosion rate of other three alloys were almost similar. The discrete second phases in Mg-1.52Zn-0.15Gd acted as severe cathodes to the matrix and accelerated the micro-galvanic corrosion whereas network shaped and uniformly distributed phases in Mg-1.52Zn-0.15Nd alloy effectively retarded corrosion. The immediate formation of Nd2O3 in the corrosion film of Mg-1.52Zn-0.15Nd alloy also contributed in improved corrosion resistance. Dominant presence of Y2O3 in Mg-1.52Zn-0.16Yalloy contributed to its better corrosion resistance.