Deciphering the role of alloying elements in spontaneous passivation by element-resolved electrochemistry: From pure metals to equiatomic CoCrFeNi

Abstract

The influence of alloying elements Co, Fe, Ni on the spontaneous passivation behavior of Cr−containing alloys (Cr = 25 at %) in 0.1 M H₂SO₄ was investigated using element-resolved electrochemistry. A bottom-up strategy was used from pure metals to quaternary alloys. The dissolution - polarization curves of pure metals showed strong correlation with that of alloys containing the corresponding elements. For most alloys, the dissolution curve closely aligns with that of the pure metal with the lowest dissolution rate at a given potential. For CoCrFeNi, Ni limits dissolution in the cathodic domain and the critical dissolution rate is determined by the overlap of Ni and Cr dissolution curves.