氮含量对新型奥氏体不锈钢电化学响应及点蚀行为的影响

Effect of Nitrogen Content on Electrochemical Response and Pitting Behavior of New Austenitic Stainless Steels

利用电化学工作站对含氮量分别为0.326%、0.527%、0.750%的新型奥氏体不锈钢在2.5%、3.5%、4.5%、5.5%、10.5%NaCl溶液中进行动电位极化测试,同时在3.5%Na Cl溶液中进行了EIS测试,获得阻抗谱图;在浓度为6%的FeCL3溶液中进行了标准点蚀试验,计算了试样的平均腐蚀速率;采用扫描电镜(SEM)与激光共聚焦显微镜(LSM)对腐蚀后试样进行三维成像观察。结果表明:试样的腐蚀电位(Ecorr)随着溶液浓度的升高,表现出先升后降的趋势,当氮含量为0.527%时,其点蚀电位(Eb)均大于1.2V;随着氮含量的增加,电荷转移电阻(Rct)以及钝化膜厚度(Lss)亦表现出先升后降的趋势,当氮含量为0.527%时获得极大值,Rct与Lss分别为4.222×10^(5)Ω·cm^(2)、6.688×10^(-8)m,说明此合金在NaCl溶液中具有最佳的耐腐蚀性。氮含量为0.527%的合金,其平均腐蚀速率以及腐蚀坑深度均具有最小值,分别为130.370 g/(m^(2)·h)、185.300μm,在相同视野下其腐蚀区域最小,耐腐蚀性良好。

The novel austenitic stainless steels containing 0.326%,0.527%and 0.750%nitrogen respectively were subjected to potentiodynamic polarization tests in 2.5%,3.5%,4.5%,5.5%and 10.5%Na Cl solutions using an electrochemical workstation.Meanwhile impedance spectra was obtained from EIS tests in 3.5%NaCl solution.The standard pitting corrosion tests were performed in 6%FeCl_3 solution to calculate the average corrosion rate of the specimens,and the corrosion morphology and three-dimensional images of the corroded specimens were observed by scanning electron microscopy(SEM)and laser confocal microscopy(LSM).The results show that the corrosion potential(E_(corr))of the specimen presents a trend of increasing and then decreasing with the increase of the solution concentration,and the pitting potential(E_b)is greater than 1.2 V when the nitrogen content is 0.527%;The charge transfer resistance(R_(ct))and passivation film thickness(Lss)also show a trend of increasing and then decreasing with the increase of the nitrogen content and the maximum value is obtained when the nitrogen content is 0.527%,the R_(ct)and Lss is 4.222×10^(5)Ω·cm^(2)and 6.688×10^(-8)m,respectively,which indicate that the alloy has the best corrosion resistance in Na Cl solution.The average corrosion rate and corrosion pit depth of the alloy with 0.527%nitrogen content have the minimum value of 130.370 g/(m^(2)·h)and 185.300μm,respectively,it has the smallest corroded area in the same field of view,exhibiting good corrosion resistance.