碳钢在模拟一级反渗透产水和海水中的腐蚀行为比较

Comparison of Corrosion Behaviors of Carbon Steel in Simulated Reverse Osmosis Product Water and Seawater

采用丝束电极测试(WBE)、电化学阻抗谱(EIS)和挂片失重法研究了静态条件下碳钢在模拟海水淡化一级反渗透(RO)产水和海水中的腐蚀形态及其电化学特性。结果表明,碳钢在模拟一级RO产水和海水中腐蚀电位随时间延长而下降;在模拟一级RO产水15d的试验中,碳钢表面微阴极、微阳极的最大电位差始终大于110mV,腐蚀过程中阴极、阳极区域位置基本不变,腐蚀始终在局部区域进行,阻抗谱显示一个时间常数;在模拟海水中2d后碳钢表面微阴极、微阳极的最大电位差小于10mV,微阴极、微阳极区域位置在不断变化,发生全面腐蚀,随着腐蚀的进行碳钢电极的电化学阻抗谱上出现Warburg阻抗,腐蚀过程逐渐发展为扩散控制,表面生成的致密腐蚀产物对碳钢的进一步腐蚀起到了一定的抑制作用,碳钢腐蚀速率下降。碳钢在模拟一级RO产水中的表观腐蚀速率略大于模拟海水,因其实际腐蚀部位面积小而局部区域的腐蚀速率比在海水中更大。

The corrosion morphology and electrochemical characteristics in simulated reverse osmosis （RO） product water and seawater were investigated by wire beam electrode （WBE）,electrochemical impedance spectroscopy （EIS） techniques and coupon weight loss method.The results show that the corrosion potential decreased with time both in simulated RO product water and seawater.In the fifteen days experiments in simulated RO product water,the biggest potential difference between micro-cathode and micro-anode on the carbon steel surface was always greater than 110 mV;the positions of cathode/anode areas were basically unchanged,and corrosion always took place on the local anode area during the experiments;the impedance spectrum of carbon steel shows one time constant.In the experiments in simulated seawater,the biggest potential difference between micro-cathode and micro-anode on the surface of carbon steel was smaller than 10 mV after two days immersion;the positions of cathode/anode areas kept changing,leading to uniform corrosion;the corrosion process began to be controlled by diffusion as the appearance of Warburg impedance in the EIS of carbon steel electrodes,which might be aroused by the compact corrosion product on the surface of carbon steel and therefore restrained the further corrosion and reduced the corrosion rate to some extent.The apparent corrosion rate of carbon steel in simulated RO product water was slightly greater than that in simulated seawater.But the actual corrosion rate on the local anode area in simulated RO product water was much more greater than that in simulated seawater due to the smaller actual corrosion area.