During the incubation and propagation periods of crevice corrosion, the hydrolysis of dissolved metal ions from stainless steel generates H⁺, which reduces the pH inside the crevice. The pH reduction causes anion migration into the crevice to maintain electrical neutrality. The addition of corrosion-inhibiting anions outside the crevice is known to be effective in reducing crevice corrosion^*1-2. Cu²⁺ cation forms a chelate complex with ethylenediaminetetraacetic acid (EDTA) and exists as the [Cu(EDTA)]^2- anion in a neutral solution. The addition of [Cu(EDTA)]^2- to NaCl solution suppresses crevice corrosion of Type 316L stainless steel. [Cu(EDTA)]^2- is an anion that migrates into the crevice and separates into Cu²⁺ and [H2(EDTA)]^2- in the low-pH environment inside the crevice, thereby inhibiting crevice corrosion.