Influence of rare earths alloying addition on the corrosion behavior of Zn in neutral aerated sodium chloride solution

The effect of rare earth metals (Gd, Dy, Er,) addition on the corrosion behavior of Zn has been investigated. The corrosion resistance of Zn99Gd1, Zn99Dy1, and Zn99Er1(at%) alloys has been assessed by open circuit potential and electrochemical impedance spectroscopy (EIS) measurements carried out in a 0.1 M NaCl solution, at approximately neutral pH, without stirring and in contact with the air. For comparison, the electrochemical tests have also been carried out on unalloyed Zn. Moreover, the surface morphology and nature of the corrosion products have been investigated. The results indicated that rare earths addition significantly improves the corrosion behavior of unalloyed Zn. This improvement is most likely due to enhanced barrier properties of the corrosion products layer and additional active corrosion protection originated from the inhibiting action of the lanthanide ions entrapped as oxides/hydroxides in this surface layer.