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

This work investigated the effects of Cu-content and passivation treatment on the corrosion resistance of Al0.3CuxCoCrFeNi (x = 0.3, 0.4, 0.5, 0.6) high entropy alloys. With increased Cu content, the Al, Cu-riched precipitates in the Al0.3CuxCoCrFeNi alloys emerged gradually, resulting in the decreased corrosion resistance and the weakening of the passive film. The passivation treatment in 30 wt% HNO3 and 1 wt% NaOH aqueous solutions promotes the Cr3+ content in the passive film of Al0.3Cu0.3CoCrFeNi 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.