3Cr低合金钢在含饱和CO_2的NaCl溶液中的腐蚀电化学行为

Effect of pH on the Corrosion and Electrochemical Behavior of 3Cr Steel in CO_2 Saturated NaCl Solution

研究了含饱和CO_2的NaCl溶液pH值对3Cr低合金钢腐蚀及其电化学行为的影响。结果表明:当NaCl溶液的pH值较低(2,3.9)时,腐蚀产物膜为单层结构,呈龟裂状;当pH值较高(6.5)时,腐蚀产物具有三层结构,外层腐蚀产物为颗粒状,内层仍呈龟裂状。NaCl溶液的pH值对3Cr低合金钢的腐蚀电化学行为也有显著影响。NaCl溶液的pH值升高能改变电极过程中的主要阴极反应,使腐蚀电位逐渐负移,且电荷转移电阻的增大使腐蚀电流密度减小。

The effect of pH value of NaCl solution on the corrosion and electrochemical behaviors of 3Cr low-alloy steel was investigated by electrochemical technique and SEM technique. The results showed that the pH value of NaCI solution had great effect on the structure of corrosion product. The corrosion scale had a monolayer and map cracking appears when pH=2 and 3.9. The corrosion product film had a triple structure when pH=6.5. The pH of corrosion media also had apparent effect on the electrochemical behaviors of the Cr low-alloy steel. With pH increasing, the main cathodic reaction of electrode process altered, resulting in the negative moving of the corrosion potential, and by the increasing of the charge transfer resistance, the corrosion current density decreased.