Étude de la réactivité et de la passivation des alliages à haute entropie

High entropy alloys (HEAs), as an emerging class of materials, have garnered significant attention in the field of materials science due to their unique multi-element compositions and exceptional performance characteristics, such as high strength, high hardness, outstanding thermal stability, and superior corrosion resistance. This study systematically investigates the factors influencing the corrosion resistance of HEAs, with a focus on analyzing the effects of exposure environments (primarily sulfuric acid solutions with varying chloride ion concentrations), external conditions (such as applied potential), and alloy composition (the influence of Mn elements). Electrochemical testing and surface analysis results indicate that chloride ions do not alter the corrosion mechanism or the thickness of the oxide film but instead affect corrosion resistance by modifying the composition of the oxide film. The increase in applied potential changes the compositional content of the surface oxide film on the Cantor alloy, particularly the content of Cr elements. Mn elements negatively impact the corrosion resistance of HEAs, affecting not only the naturally passive film but also the passive film formed during repassivation; however, the underlying mechanisms require further investigation. Additionally, by combining electrochemical equipment with capillary techniques, this study monitored the formation process of single pit, providing a deeper understanding of the mechanisms of pit development at different stages and the influence of applied potential. The applied potential consistently accelerates the initiation of pit and repassivation by increasing the kinetic constants of the alloy dissolution reaction and oxide film formation reaction; however, it does not play a role during the stable propagation of pit.