海洋环境下三电极的电偶腐蚀仿真

为研究三电极的电偶腐蚀行为，测量了CF8611/AC531复合材料（CFRP）、7B04-T74铝合金（7B04）和镀锌30CrMnSiA钢（GSB）的极化曲线；开展了搭接件在模拟海洋环境下的全浸试验；设计了圆形三电极，推导了稳态腐蚀场和参数化扫描方程，建立了三电极和搭接件的电偶腐蚀模型。结果表明：稳态腐蚀场中的电势分布符合Laplace方程；电位最高的CFRP为阴极，最低的GSB为阳极，中间的7B04阴/阳极角色会随某一电极面积变化而转变，给出了转变的临界面积比，各电极表面电偶电流服从指数分布，相关系数近于1，拟合精度高；在搭接件中，搭接区电位和电流密度最高，并向两端对称递减，7B04和GSB均为阳极，电流密度分别提高约210倍和328倍，电偶腐蚀效应显著；搭接区7B04板全面腐蚀，厚度损失约1.011%；仿真所得点蚀敏感区宽度范围为3.9~7.6mm，实测所得宽度范围为4.667~8.872mm，二者范围、形状及变化规律吻合较好，表明模型有效、可靠。

Simulation of galvanic corrosion of three electrodes in marine environment

To study the galvanic corrosion behavior of three electrodes, polarization curves of CF8611/AC531 composite (CFRP), 7B04-T74 aluminum alloy (7B04) and galvanized 30CrMnSiA steel (GSB) were measured. Full immersion test of the lap joint in the simulated marine environment was carried out. The circular three electrodes were designed, the steady-state corrosion field and the parameter scanning equation were deduced, and the galvanic corrosion model of the three electrodes and the lap joint were established. The results show that the potential distribution in the steady-state corrosion field accords with the Laplace equation. CFRP with the highest potential is cathode; GSB with the lowest is anode; the cathode or anode role of 7B04 is not fixed, it varies with the area of arbitrary electrode, and the critical area ratio is given out. The galvanic current of each electrode obeys the exponential distribution, and the correlation coefficient is approximately 1, which indicates a high fitting precision. On the lap joint, the potential and current density at the overlap are the highest and they descend symmetrically to both ends. 7B04 and GSB are anodes and the current density of them increases by about 210 and 328 times separately. This shows that the galvanic corrosion effect made by CFRP is very significant. The corrosion type of 7B04 plate at the overlap is general corrosion, and the thickness of about 1.011% loses. The simulation value of the distance of the pitting sensitive area is 3.9-7.6 mm and the measured value is 4.667-8.872 mm. The range, shape and change rule of the two are in good agreement. This illustrates that the model is effective and reliable.