Spontaneous passivation of the CoCrFeMnNi high entropy alloy in sulfuric acid solution: The effects of alloyed nitrogen and dissolved oxygen

The dissolution and passivation kinetics of CoCrFeMnNi high entropy alloys with and without nitrogen addition in 0.1 M H2SO4 were investigated by element-resolved electrochemistry to follow the passivation quasi in situ. The nitrogen containing alloy exhibited spontaneous passivation driven by dissolved oxygen. The alloy without nitrogen did not passivate spontaneously under the same conditions, and its dissolution was accelerated by increasing the dissolved oxygen. This was attributed to an enhanced efficiency of passivation for the nitrogen containing alloy with a lower critical dissolution rate. Both spontaneous and anodic passivation were accompanied by significant Cr accumulation on the surface.

Automated summary

In this study, the dissolution and passivation kinetics of CoCrFeMnNi high entropy alloys in an acidic solution were investigated. The alloy with nitrogen addition exhibited spontaneous passivation driven by dissolved oxygen, while the alloy without nitrogen required an acceleration of dissolved oxygen for passivation. The nitrogen containing alloy had a lower critical dissolution rate, leading to enhanced passivation efficiency.