Investigation of the ordered and disordered corrosion morphologies on Ni-based alloy in the passive state

We report an order and disorder combined corrosion morphology of dual-phase Ni-based alloy in the passive state. After galvanostatic polarization in the passive region, the surface of the γ(Ni) phase presents amorphous feature while that of the γʹ(Ni3Al) phase maintains crystalline. The variations in weight percentages of Ni (50.19% → 3.80%), Co (19.24% → 0.65%), Ta (0.85% → 21.19%), and W (5.73% → 43.79%) of γ surface are evident, whereas the composition of γʹ surface is nearly unchanged. The passive film comprises Wox6+, Taox5+, Crox3+, Coox8/3+, Nihy2+, and Cohy2+, and it shows stronger protection effect on the γ phase.