316L不锈钢在溶有不同气体NaCl溶液中的点蚀敏感性

Pitting Susceptibility of 316L Stainless Steel in NaCl Solution with Different Dissolved Gases

分别采用动电位法和恒电位法得到了316L不锈钢在溶有不同气体(CO2、N2、O2、H2S+CO2、H2S)NaCl溶液中的阳极极化曲线和I-t曲线,并研究了316L不锈钢的点蚀敏感性以及蚀坑的形貌、蚀坑处的元素分布。结果表明:溶解气体对316L不锈钢点蚀敏感性影响从小到大的顺序为CO2、N2、O2、H2S+CO2、H2S;当H2S与CO2两种气体以1…1的体积比共存时,点蚀主要受H2S控制;点蚀优先在316L不锈钢中铝的氧化物处萌生,该处铬、钼、镍耐蚀合金元素含量的下降有利于蚀坑的进一步发展。

The anodic polarization curves and current-time curves of 316 Lstainless steel in NaCl solution with different dissolved gases,such as CO2,N2,O2, H2S＋ CO2 and H2 S,were obtained by potentiodynamic polarization and potentiostatic polarization test methods respectively,the pitting susceptibility of 316 Lstainless steel was studied,as well as the morphology of the corrosion pits and element distribution in the corrosion pits.The results show that the increasing order of pitting susceptibility of 316 Lstainless steel influenced by dissolved gases was CO2,N2,O2,H2S＋CO2and H2 S.The pitting of 316 Lstainless steel was mostly controlled by H2 S when the volume ratio of H2 S to CO2 was 1：1.The pitting was prior to nucleation at the location of Al-oxide in 316 Lstainless steel,and the corrosion pit further developed because of the decrease of Cr,Mo and Ni contents around inclusions location.