New zinc-rare earth alloys: Influence of intermetallic compounds on the corrosion resistance

New ZnRE 1-2 wt.% alloys (RE = Ce, La and Mischmetal) were synthesized. Microstructural analyses reveal that rare-earth metals are exclusively present in intermetallic phases contained within the zinc matrix: CeZn11 or LaZn13 in binary alloys; Ce1−xLaxZn11 and CeyLa1−yZn13 in Zn-Mischmetal alloys. This phase equilibrium is confirmed by a thermodynamic description of the Zn-rich corner of Zn-Ce-La system. Both intermetallic phases CeZn11 and LaZn13 induce a cathodic inhibition of the corrosion of the Zn-RE alloys in comparison with pure zinc. In the specific case of cerium addition, a significant anodic inhibition is also observed.