Experiment and simulation of the galvanic corrosion of trimetallic couple under thin electrolyte film condition

The effects of thin electrolyte film thickness, corrosion product, and electrode size on the galvanic corrosion of 2024/Q235/304 trimetallic couple under thin electrolyte film conditions are investigated by experiments and the finite-element method (FEM) model. Galvanic current curves were measured by zero resistance ammeter. A FEM model was built and validated with considering the electrochemical reaction, the mass transfer, deformation of anode, and deposition of corrosion products, without considering the electrolyte evaporation. It is found that the reduction of thin electrolyte film thickness plays dual roles, that is, decreasing the oxygen diffusion path to accelerate galvanic corrosion and increasing the solution resistance to inhibit galvanic corrosion. The cathode/anode roles of Q235 with medium corrosion potential among three metals are different at its different locations due to the effect of the IR drop of solution resistance. The deposition of corrosion products inhibits the galvanic corrosion, but aggravates the edge effect in the junction between 2024 and Q235.