结合WBE与EIS技术研究环氧涂层下碳钢与铜合金在海水中的电偶腐蚀  

Studies of Galvanic Corrosion of Carbon Steel/Copper Alloy Couple under Epoxy Coating Exposed to Seawater Using WBE and EIS Techniques

作　　者：李钊 王玲[2] 刘杰 牟献良[2] 陆忠海 LI Zhao;WANG Ling;LIU Jie;MU Xian-liang;LU Zhong-hai(College of Chemistry and Chemical Engineering, Yantai University, Yantai 264005, China;Weathering Test and Research Center of Science Technology and Industry for National Defense,Southwest Technology and Engineering Research Institute, Chongqing 400039, China)

机构地区：[1]烟台大学化学化工学院,山东烟台264005 [2]西南技术工程研究所国防科技工业自然环境试验研究中心,重庆400039

出　　处：《表面技术》2019年第6期299-305,共7页Surface Technology

基　　金：装备预研船舶重工联合基金项目(6141B04080206);山东省自然科学基金项目(ZR2016BQ15);国防技术基础项目(JSHS2015209C003&JSHS2015209B001)~~

摘　　要：目的研究环氧涂层下碳钢与铜合金在海水中的电偶腐蚀行为及涂层整体和局部区域的劣化过程。方法使用丝束电极(WBE)技术和电化学阻抗谱(EIS)技术研究丝束电极表面的电流密度分布和涂层阻抗谱演化,同时对比分析碳钢区域与铜合金区域涂层的阻抗谱特征。结果阳极电流峰首先出现在碳钢局部区域,而电流密度较大的阴极电流峰主要集中出现在铜合金区域的边缘。当浸泡至122 h时,铜合金区域的涂层阻抗明显低于碳钢区域的涂层阻抗,且EIS响应出现了Warburg扩散阻抗特征。在浸泡456 h后,单根钢电极发生由阴极向阳极的极性转换。结论涂层下碳钢与铜合金在海水中发生电偶腐蚀时,铜合金作为阴极被保护,但铜合金区域的涂层在阴极剥离的作用下加速劣化。在涂层劣化过程中,碳钢区域的涂层缺陷处成为腐蚀反应的阳极区,而主要的阴极区位于铜合金的边缘区域,这与溶解氧的“竞争效应”有关。由于涂层发生阴极剥离现象使得基底金属被腐蚀,从而导致涂层下单根钢电极的电流发生由阴极向阳极的极性转换。The work aims to study the galvanic corrosion behaviors of carbon steel/copper alloy couple under epoxy coating and the degradation process of the whole and local area of the coating exposed to seawater. The current density distributions of the WBE and the EIS evolution of the coating on WBE surface were studied by WBE and EIS techniques. Meanwhile, the EIS characteristics of the coating on carbon steel and copper alloy surface were also compared and analyzed. It showed that the anodic current peak first appeared at the local area of carbon steel, while the cathodic current peaks with larger current densities appeared at the edge of the copper alloy area. After 122 h of immersion, the impendence value of the coating on copper alloy surface was obviously lower than that of the coating on carbon steel surface, and the Warburg impedance behavior could be observed in the EIS of the coating on copper alloy surface. The current of the single steel electrode changed from cathodic to anodic when the WBE was immersed for 456 h. In conclusion, when the carbon steel and copper alloy under epoxy coating were electrically coupled in seawater, the copper alloy was protected by carbon steel from corrosion but the degradation processes of the coating on copper alloy surface was accelerated by cathodic delamination. During the degradation processes of the epoxy coating, the local defect area of the coating on carbon steel surface became the anodic area and the main cathodic area was concentrated at the edge of copper alloy area, which was related to the “competition effect” for dissolved oxygen. The reason of the polarity reversals from cathodic to anodic of the single carbon steel electrode may be that the metal was corroded because of cathodic delamination.

关 键 词：丝束电极 电化学阻抗谱 环氧涂层 海水 碳钢 铜合金 电偶腐蚀 

分 类 号：TG172.5[金属学及工艺—金属表面处理]