Corrosion and passivation behavior of FeCoCrNiNbx eutectic high-entropy alloys in H2SO4 solution

The bilayer structure passive films were formed on FeCoCrNiNbx alloy surfaces in 0.5 M H2SO4 solution. The inner film was denser and more protective. The high Cr/Nb ratio would facilitate the passivation of FeCoCrNiNbx alloys and the formation of a thicker passive film on the alloy surface. The protective ability of the passive film was determined by the structure, composition, and thickness of the passive film, while semiconductor characteristics of the passive film could only contribute to the improvement of the protective ability of the passive film, but could not directly determine the protective ability of the passive film.