Corrosion of the grounding grid is the most defective parameter, which has an appreciable effect on the grounding grid performance and its ability to ensure its main target of stability and safety of the electrical systems. The mathematical model is used to investigate the corrosion degree of the grounding grid, and its effect on the grid current distribution and the grounding grid lifetime. The study is applied to different shapes of steel grounding grids buried in two layers of soil. Moreover, an experimental study is carried out to investigate the relationship between the corrosion degree and the contact resistance of the galvanized steel grounding grid for different shapes at low resistivity conditions.