多电极偶接对金属大气腐蚀影响的试验与仿真

搭建薄液膜厚度测量与控制装置，采用微距参比电极后置法组建三电极体系，测量了厚度为100 μm的3.5wt% NaCl液膜下2A12铝合金、TC18钛合金和30CrMnSiNi2A高强钢的极化曲线和耦合体系的电偶电流；建立了基于薄壳电流分布的Comsol腐蚀仿真模型，得到了100 μm液膜下电极电位分布和电流密度分布图，通过对电极表面进行局部电流面积分计算得到了其电偶电流，对不同电极进行了面积的参数化扫描，讨论分析了不同面积比对于电偶电流的影响。结果表明：利用仿真模型得到的电偶电流值与试验值吻合较好，在2A12/30CrMnSiNi2A/TC18多电极体系中2A12充当阳极，TC18/30CrMnSiNi2A充当阴极，且阴阳极极性不随面积比的变化而发生转变，电偶电流主要集中在30CrMnSiNi2A与2A12之间，电偶电流与TC18面积呈线性关系，其对数与2A12和30CrMnSiNi2A面积的对数之间呈线性关系。利用建立的仿真模型对模拟搭接件大气腐蚀进行了仿真研究，仿真发现垫圈、2A12与30CrMnSiNi2A偶接接缝处及2A12与TC18偶接铆钉处电流密度分布更为集中，易发生腐蚀，与暴晒试验结果相符，说明该仿真模型对于多电极偶接的腐蚀分布具有很好的预测作用。

Test and simulation of effects of multi-electrode coupling on atmospheric corrosion of metals

A device for measuring and controlling the thickness of thin electrolyte layer is set up. Using post-macro reference electrode to form three electrode system, the polarization curves and galvanic current of the coupling system of 2A12 aluminum alloy, TC18 titanium alloy and 30CrMnSiNi2A high strength steel are measured under 100 μm 3.5wt%NaCl electrolyte layer. By the established Comsol corrosion simulation model based on the shell current distribution, the potential distribution and current density distribution of the electrode of 100 μm thin electrolyte layer are obtained.The galvanic current is got by surface integral of the electrode. Parametric scanning is performed for different electrode areas, and the influence of different area ratios on galvanic current is discussed. The result shows that the galvanic current value obtained by the simulation model agrees well with the experimental data. In the 2A12/30CrMnSiNi2A/TC18 multi-electrode system, 2A12 acts as an anode and TC18/30CrMnSiNi2A acts as the cathode.Moreover, the polarity of cathode and anode does not change with the change of area ratio.The galvanic current mainly concentrates between 30CrMnSiNi2A and 2A12.The galvanic current is linearly related to the area of TC18 and its logarithm is linear with the logarithm of the area of 2A12 and 30CrMnSiNi2A. Using the simulation model established in this paper, the atmospheric corrosion of designed lap joints is simulated. The simulation result shows that current density distribution is more concentrated at the washer, the joint of 2A12 and 30CrMnSiNi2A, the rivet on the junction of 2A12 and TC18, and corrosion is easy to occur in these areas. The result is consistent with the results of exposure test, showing that the simulation model has a good prediction of corrosion distribution of multi-electrode couples.