Pitting corrosion of 4Cr13 steel in a chlorine tank

Abstract

Abstract Pitting corrosion is harmful and often occurs in chloride solution. The pitting corrosion of 4Cr13 steel in a chlorine tank was investigated in this study. Cr-depleted rings were observed and the Cr-depleted ring coincided with the bumps consisting of corrosion product. Carbides distributed along the Cr-depleted ring were also observed. Many pitting with spherical or shallow shapes were observed by cross-section morphology exam. The depth of pitting for Sample A is smaller than that for Sample B which accorded with surface morphology. The corrosion product was composed of a Fe-rich outer layer and a Cr-rich inner layer. The Fe-rich outer layer will rapture and fall off with the increase of corrosion products, and then the Cr-rich inner layer was revealed. As a result, Cr-depleted rings were inspected with SEM-EDS. The pitting corrosion mechanism of 4Cr13 steel in the chlorine tank was also discussed.