The Anodic Role of Ni-Containing LPSO Phases During the Microgalvanic Corrosion of Mg98Gd1.5Ni0.5 Alloy

In the present study, the corrosion characteristics of cast Mg98Gd1.5Ni0.5 alloy with Ni-containing long-period stacking ordered (LPSO) structures were investigated. The results reveal that the Ni-containing LPSO phases were more active than the Mg matrix and preferentially eroded during the immersion process. This behavior indicates that the Ni-containing LPSO phases could have acted as microanodes, in contrast to the cathodic role of the Ni-free LPSO phases in other Mg alloys. Furthermore, the potential difference of approximately 600 mV between the phases accelerated the dissolution rate of the LPSO phase. Corrosion of the Mg matrix also occurred due to the inhomogeneous microstructure of the matrix. The synergetic corrosion between the Ni-containing LPSO phases and the enrichment of Cl− in the thick corrosion product films dominated the propagation of corrosion, which substantially deteriorated the corrosion resistance and accelerated the corrosion process of the Mg98Gd1.5Ni0.5 alloy.