Effects of Cu-content and passivation treatment on the corrosion resistance of Al0.3Cu CoCrFeNi high-entropy alloys

Abstract

This work investigated the effects of Cu-content and passivation treatment on the corrosion resistance of Al 0.3 Cu x CoCrFeNi ( x = 0.3, 0.4, 0.5, 0.6) high entropy alloys. With increased Cu content, the Al, Cu-riched precipitates in the Al 0.3 Cu x CoCrFeNi alloys emerged gradually, resulting in the decreased corrosion resistance and the weakening of the passive film. The passivation treatment in 30 wt% HNO 3 and 1 wt% NaOH aqueous solutions promotes the Cr 3+ content in the passive film of Al 0.3 Cu 0.3 CoCrFeNi and reduces the probability of pitting initiation, which substantially increased the corrosion resistance of the alloy. However, this treatment became less effective as the continuously intensified Al, Cu-riched precipitates which damaged the formation of homogeneous passive film and caused more serious galvanic corrosion. • Al 0.3 Cu x CoCrFeNi is FCC, the Al, Cu-riched precipitates increased with increasing Cu. • The passivation treatment is effective to promote growth of passive film on the HEAs. • The passivation effect is diminished as the Cu increased in the Al 0.3 Cu x CoCrFeNi. • The severe Al, Cu-riched precipitates destroy passive film and cause galvanic corrosion.