Modeling the effect of residual and diffusion-induced stresses on corrosion at the interface of coating and substrate

The effect of residual and diffusion-induced stresses on corrosion at the interface of coating and substrate has been analyzed within a multidisciplinary approach, i.e., material science, solid mechanics, and electrochemistry. A self-consistent equation for corrosion current density, involving the combined effect of residual stress and diffusion-induced stress is developed. The influences of temperature, moduli ratio, thickness ratio, thermal mismatch ratio, and residual stress gradient of coating and substrate on the corrosion current density are then discussed. Results indicate that when the thermal expansion of coating is greater than substrate, the decrease in temperature from fabrication temperature accounts for the same direction of both the residual and the diffusion stresses. This behavior increases the deflection of the coating-substrate system and results in the evolution of tensile residual stress in the coating. The tensile stress opens the pre-existing coating microcrack, allowing the diffusion of corrosive agents and therefore, accelerating the corrosion damage to the coating/substrate interface. The model is based on experimental observations conducted to understand the behavior of corrosion at the coating/substrate interface in the presence of tensile or compressive residual stresses. At the end, the model was validated against the experimental results showing a good quantitative agreement between the predicted theoretical and experimental trends.