Influence of Solution Alkalinity and Alternating Current Density on Anti-corrosion Property of CoCrFeMnNi High-Entropy Alloy in Simulated Concrete Pore Solution

This paper comprehensively evaluated the effect of solution pH and alternating current (AC) on the corrosion behavior of CoCrFeMnNi high-entropy alloy (HEA) in simulated concrete pore solution. The results indicate that increased solution pH markedly enhances the corrosion rate of the HEA and the number and size of pits as well as more flaws are produced inside its thinned passive film, which suggests that the anti-corrosion property of the HEA is reduced. Under strong solution alkalinity, the rough passive film on the HEA is uneven and unstable, which significantly weakens the protection of the film. As iAC augments, more oxygen vacancies are generated to absorb anions in test solution and Ep shifts negatively, which decreases the stability of passive film and promotes the pitting sensitivity. Moreover, the synergistic influence of pH value and AC density reflected by a remarkable increase of ip facilitates the dissolution of passive film and declines the corrosion resistance of the HEA, which may be due to the reason that increased AC interference produces more OH- ions.