Application of Laplace Equation-Based Modeling into Corrosion Damage Prediction for Galvanic Coupling Between a Zinc Plate and Stainless Steel Rods Under a Thin Film Electrolyte

Connections between dissimilar materials are frequently encountered in aviation and marine structures. When two types of materials are exposed to a moist atmospheric condition, there is a high possibility that a corrosion cell can be established due to galvanic coupling via the creation of either a droplet or a thin film electrolyte. Experimental measurements under such conditions are challenging. Computational modeling can complement experimental characterization to achieve a better understanding of corrosion susceptibilities and the dependence on external variables in atmospheric conditions. In this work, a finite element modeling approach based on the Laplace Equation with mathematically fitted electrochemical kinetics from an experiment was developed to simulate the electrochemical and corrosion damage distributions along a zinc (Zn) plate with inserted stainless steel (SS) rods under thin film electrolyte conditions. Modeling results were then compared with accelerated exposure testing results to demonstrate the ability of Laplace Equation-based modeling to predict corrosion damage under thin electrolyte conditions. Comparison of modeling and measurement of damage along the Zn plate and showed the effective electrolyte layer thickness was about 3,500 μm on the surface during modified ASTM B117 test assuming a constant thin electrolyte layer was maintained on the surface during the exposure.