高氮奥氏体不锈钢的临界点蚀温度及Cl^-浓度对其的影响

Critical Pitting Temperature of High Nitrogen Austenitic Stainless Steel and Effect of Cl^- Concentration on It

为了测定高氮奥氏体不锈钢(HNS)在3.5%(质量分数) NaCl溶液中的临界点蚀温度(CPT),采用电化学阻抗和动电位极化曲线方法测量出了HNS在NaCl溶液中CPT的大致范围,再通过恒电位极化法确定了CPT的具体值,同时考察了Cl-浓度对CPT的影响,通过金相显微镜进一步验证了CPT的准确性。结果表明:在70~75℃范围内,电化学阻抗容抗弧明显减小,电荷转移电阻Rct大幅度降低。动电位极化曲线表明,在70~75℃击破电位出现明显降低,恒电位极化方法确定HNS的CPT为71.2℃。同时,当NaCl溶液浓度从3.5%增加到20%时,其CPT由71.2℃下降至66.5℃。

In order to determine the critical pitting temperature（CPT） of high nitrogen austenitic stainless steels（HNS） in 3.5%（mass fraction） NaCl solution, the CPT range of HNS in NaCl solution was measured by electrochemical impedance spectroscopy and potentiodynamic polarization curves, and the specific temperature of CPT was determined by potentiostatic polarization method, and the effect of Clconcentration on CPT was also investigated, and the accuracy of CPT was further verified by optical microscope. The results showed that there was a large decrease of the capacitive arc diameter and the charge transfer resistance Rctat the range of 70-75 ℃. The break potential from the potentiodynamic polarization curve also displayed a significant decrease at 70-75 ℃. The CPT determined from potentiostatic polarization curve was 71.2 ℃, and at the same time, it was found that the CPT decreased from71.2 ℃ to 66.5 ℃ as the NaCl concentration increased from 3.5% to 20%.