Oxide MnCr2O4 induced pitting corrosion in high entropy alloy CrMnFeCoNi

Composition and structure of the oxide and its effect on corrosion property in the high entropy alloy CrMnFeCoNi have not been revealed so far. In the present work, oxide in CrMnFeCoNi is identified as MnCr2O4 using transmission electron microscopy. Moreover, the oxide MnCr2O4 is detrimental to pitting resistance indicated by comparison study of CrMnFeCoNi with and without the oxide. This is because that the pitting prefers originating from MnCr2O4/matrix interface, in other words, the matrix around oxides dissolves more easily. From the viewpoint of corrosion, MnCr2O4/matrix forms a local galvanic cell, and the matrix as an anode dissolves quickly.