Fig. 17: Polycrystalline material in contact with a corrosive environment highlighting the diffuse interface between the liquid (ϕ = 0) and solid (ϕ = 1) phases.

The GBs possess a heightened diffusivity Dgb compared to the metal grain Dmg via an additional parameter that differentiates between grain boundary (η = 1) and metal grain (η = 0). The corrosion mechanism is based on the bulk diffusion of Cr toward the exposed surface.