Electrochemical Corrosion and Critical Pitting Temperature of S32750 Super Duplex Stainless Steel in NaCl Solution

Abstract

The electrochemical corrosion behavior and critical pitting temperature (CPT) of S32750 super duplex stainless steel in 3.5%NaCl solution were investigated by electrochemical techniques. The morphologies of the steel before after pitting corrosion were observed by scanning electron mi- croscope. The CPT of the S32750 steel was identified as 71 ℃. A passive film could form on the steel surface when the solution temperature was below the CPT. While, when the solution tempera- ture was above the CPT, pitting corrosion occurred on the steel surface as the result of the break- down of the passive film due to the increase of the Cl - activity. Pitting corrosion became more seri- ous with the increasing temperature. Moreover, the corrosion models of the steel below and above the CPT were sketched respectively.