A simple model for the effect of intergranular corrosion on overall corrosion processes is investigatedusing a cellular automata approach. The corroding polycrystalline material consists of domains and theirboundaries. The domains represent the monocrystalline cores while their boundaries represent the inter-granular defects. Either, a periodic pattern or randomly generated domains of Voronoï tessellation areused to represent the polycrystalline structure. The parameters of the model, taking into account thepolycrystalline aspect of corrosion, are the domain density and the corrosion probabilities of metal graincore and grain boundary sites. The corrosion probability for grain boundary is set to a value higher thanit is for the grain core. A complex surface structure appears with a high geometrical roughness whendefects are not too dense. A strong correlation is established between the roughness evolution, the metalcrystalline properties and the corrosion mechanism of metal dissolution. This work concerns simulationsin 3D and extends the previous work limited to 2D simulations.