Selective corrosion mechanism of CoCrFeMoNi high-entropy alloy in the transpassive region based on the passive film characterization by ToF-SIMS

The selective corrosion mechanism of CoCrFeMoNi HEA in the transpassive region is investigated by electro-chemical tests and ToF-SIMS. The results show that Mo and Cr oxides are more enriched in the local passive films formed on the mu and sigma phases than those formed on the FCC phase. As the applied potential increases, the passive film thickens, while the Mo and Cr content decreases, which results in the passive film degradation. The local passive films formed on the FCC surface is easier to dissolve in the transpassive region than those formed on the mu and sigma phases due to the lower content of Cr and Mo in the FCC films. Therefore, selective corrosion of FCC phase occurs in the transpassive region.