The anti-pitting mechanism of the CoCrFeMnNi alloy, which is susceptible to chloride conditions despite containing ca. 20 wt.% Cr, was investigated. It revealed that the Cr-depletion caused by MnO·Cr2O3, which is formed by the two principal elements, is to blame for its poor anti-pitting properties. The methods of adding Si, Al, and Ti for removing the Cr-depletion were proposed with a deep understanding of the general mechanism. The effectiveness of the methods originates from lower Gibbs formation energies of the Si, Al, and Ti oxides than that of MnO·Cr2O3, which inhibits Cr diffusion. Overall, the result presents a promising solution for removing Cr-depletion that may be commonly formed in high entropy alloys.