pH值对Q235碳钢与304L不锈钢在典型含硫环境中电偶腐蚀行为的影响

采用电化学法和浸泡法研究了Q235碳钢与304L不锈钢在典型含硫环境中的电偶腐蚀行为。采用SEM观察试样表面形貌。结果表明：在实验体系中304L的阴阳极过程均为电化学活化步骤控制；在pH为4和7的实验溶液中,Q235钢的阴阳极过程均受电化学活化控制；而在pH=13.3的实验溶液中,Q235阴极过程受电化学过程控制,阳极过程受离子扩散控制。在三种实验溶液中的电偶腐蚀效应随阴阳极面积比的增大而增大,但电偶电流随阴阳极面积比的变化并不呈现出对数正比规律。随着溶液pH值的升高,Q235钢的电偶腐蚀速率明显减小,但电偶腐蚀效应变化不明显。

Effect of pH value on the galvanic corrosion behaviour of Q235-304L couples in sulfur environment

The galvanic behaviour of a Q235-304L couple was studied by the electrochemical method and immersion test. Surface morphologies of the samples were observed by SEM after rust cleaning. The results showed that both the cathodic and anodic processes of 304L were controlled by the electrochemical activation step in all the three solutions with pH values of 4.0, 7.0 and 13.3, and both the cathodic and anodic processes of Q235 in the solutions with pH values of 4.0 and 7.0 were controlled by the electrochemical step, while the anodic process of Q235 exhibited an apparent characteristics of diffusion control when the pH value of the solution was 13.3. As the area ratio increases, the galvanic effect increased in all the three solutions accordingly, but the correlation between the galvanic current and the cathode/anode area ratio did not accord to the rule of logarithm. With the elevation of pH value, the galvanic corrosion rate of Q235 would greatly decrease, but the change of the galvanic effect was not so obvious.