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

    • 摘要: 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% NaCl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,RctLss分别为4.222×105 Ω·cm2、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/(m2·h)、185.300 μm,在相同视野下其腐蚀区域最小,耐腐蚀性良好。

       

      Abstract: 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% NaCl 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%FeCl3 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(Ecorr) of the specimen presents a trend of increasing and then decreasing with the increase of the solution concentration, and the pitting potential(Eb) is greater than 1.2 V when the nitrogen content is 0.527%; The charge transfer resistance (Rct) 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 Rct and Lss is 4.222×105 Ω·cm2 and 6.688×10-8 m, respectively, which indicate that the alloy has the best corrosion resistance in NaCl 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/(m2·h) and 185.300 μm, respectively, it has the smallest corroded area in the same field of view, exhibiting good corrosion resistance.

       

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