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.
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