Corrosion is one critical type of damage in metallic composite, in which pitting corrosion further disables the anti-corrosion ability of multi-layer composite. The current trend of additive manufacturing brings a possibility to perform composite design with microscopic leading, leading to a demand to improve the existing numerical methods to prepare structural coordinates data before manufacturing. This paper presents a proposal to merge the computational techniques of metallic grain microstructure formation and diffusion-control corrosion for the realistic simulation of microstructural corrosion resistance. Powder-based microstructures described by 4th-order molecular density tensors were investigated in compression with previous homogeneous models. Digital characterizations including surface area, surface roughness and continuity were proposed to simulate the property deterioration caused by pitting corrosion. It is found that the grain boundary plays a critical role in structural resistivity to corrosion, providing a computation insight into corrosion damage prevention for metallic composite with visualized four-dimensional data.