S32750超级双相不锈钢在NaCl溶液中的临界点蚀温度及电化学腐蚀机理

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

采用电化学测试研究了S32750超级双相不锈钢在3.5%Na Cl溶液中的临界点蚀温度(CPT)及电化学腐蚀机理,结合试样点蚀前后的形貌变化,得出S32750不锈钢的临界点蚀温度为71℃。在低于临界点蚀温度时,不锈钢表面能形成稳定的钝化膜;高于临界点蚀温度时,由于Cl-的活性增加及钝化膜的溶解,不锈钢表面产生点蚀现象,且温度越高,点蚀越剧烈。构建了双相不锈钢S32750临界点蚀温度前后的电化学腐蚀模型。

The electrochemical corrosion behavior and critical pitting temperature(CPT) of S32750 super duplex stainless steel in 3.5%Na Cl solution were investigated by electrochemical techniques.The morphologies of the steel before after pitting corrosion were observed by scanning electron microscope. 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 temperature was above the CPT, pitting corrosion occurred on the steel surface as the result of the breakdown of the passive film due to the increase of the Cl-activity. Pitting corrosion became more serious with the increasing temperature. Moreover, the corrosion models of the steel below and above the CPT were sketched respectively.