Role of alloyed Nd in the microstructure and atmospheric corrosion of as-cast magnesium alloy AZ91

The influence of Nd on the atmospheric corrosion performance of AZ91 alloy was evaluated as per PV1210 standard. Additionally, immersion and electrochemical measurements were carried out. The beneficial effect of Nd is associated with: (i) suppressed galvanic corrosion between α-Mg and secondary phases, (ii) refined β-phase morphology and (iii) increased proportion of carbonates in the outer surface layer. In case of atmospheric corrosion, the role of β-phase is the least important factor out of the three. The optimum Nd content is 0.5 wt.%. Further additions do not improve significantly the corrosion performance.