Prevention of Crevice Corrosion by Infiltrating Pure Water

Abstract

Crevice corrosion occurs when the concentration of chloride or hydrogen ions in the solution inside the crevice exceeds the critical levels at which the passive metal begins to be depassivated. Therefore, if pure-water is injected into a crevice through a permeable gasket, their concentration might be kept below the critical levels. In this study, the applicability of this pure-water infiltration method to preventing crevice corrosion of flanges in salt production plants was investigated. The crevice-corrosion susceptibility of a type-316 specimen with about 10 mm of effective crevice length was evaluated from the repassivation potential for crevice corrosion (E_{R, CREV}). A paper-filter disk was inserted as the permeable gasket in the crevice. A simulated concentrated brine at 70°C was used for the test solution-The E_{R, CREV} when the pure-water was injected was 80 mV nobler than that measured without the infiltration. The 80 mV shift of the E_{R, CREV} to the noble direction is the equivalent of making the solution's pH increase by 1.2, theoretically. This result suggests that crevice corrosion can be prevented effectively by applying the pure-water infiltration method.