Understanding the fundamental behaviors of tribocorrosion for metals is critical for their possible application in seawater. For the recently emerging medium entropy alloys (MEAs), while mechanical wear and corrosion phenomena have been established, such experimental exploration is still lacking regarding the tribocorrosion behavior. In this work, the tribocorrosion behavior of CoCrNi MEA was investigated on a reciprocating sliding friction testing machine. Although a significant increase of

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... rent density formed due to sliding, CoCrNi exhibits superior passivity when compared with 316L and Inconel 600. In addition, the total tribocorrosion volume loss increases with positive shifting of the applied potential for CoCrNi. Specifically, the total material loss at an applied potential more positive than the pitting potential is one order in magnitude larger than that under pure mechanical wear, confirming the synergy between wear and corrosion. The generated pits on the worn surface became the preferred locations of wear and tear, leading to accelerated materials' loss rate. Through detecting the morphologies of the contact surfaces, the features of abrasive wear, adhesive wear, delamination, and plastic deformation were revealed for CoCrNi during tribocorrosion at different potentials.