饮用水水质对缺陷涂层腐蚀行为的影响

目的研究带缺陷环氧富锌涂层在不同水质的饮用水模拟溶液中的腐蚀机理,为饮用水输水管内壁涂层的选用提供建议。方法采用电化学阻抗谱(EIS)研究涂层浸泡过程中的电化学行为,分别采用扫描电子显微镜(SEM)、EDS能谱仪和拉曼光谱对腐蚀产物的形貌和成分进行分析。结果在含Ca2+较多的溶液中,缺陷处形成了致密的水垢,并在水垢附近形成了双层锈结构;在含Ca2+较少的溶液中,垢的生长受到限制,缺陷处布满黄锈,并且起泡现象严重。结论涂层在硬度较小的溶液中具有更好的抗渗性;而在硬度较大的溶液中更容易形成粗大而紧密堆积的碳酸钙柱状晶,覆盖在缺陷处形成水垢,阻碍涂层的阴极剥离和阴极起泡过程。对于输送软水的饮用水管道,内壁涂层的防划伤是关键;对于输送硬水的饮用水管道,内壁涂层的抗渗能力是关键。

Effects of Drinking Water Hardness on Corrosion Mechanism of Defected Coating

Objective The corrosion mechanism of defected zinc rich epoxy coating was studied in simulated drinking water with different hardness, which will be valuable for the selection of the coating used in the inner wall of drinking water pipes. Methods The electrochemical behavior of the coating during the immersion was studied by electrochemical impedance spectroscopy (EIS). The morphology and composition of corrosion products were investigated by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and Raman spectra. Results The results showed that the sample immersing in the solution containing higher concentration of Ca2+ were protected by incrustation covering the defect, which delayed the process of cathodic disbonding. In the solution containing lower concentration of Ca2+, the coating blistered around the defect because of the loose accumulation of the corrosion products. Conclusion The coating had better permeability resistance in soft water while had better cathodic disbonding resistance in hard water. Some suggestion for the application of coatings in drinking water was given at last.