We propose a combined model investigating the interplay between a growing biofilm on a metallic surface and environmental suported stress corrosion. The biofilm model incorporates both substrate diffusion, bacteria metabolism and biofilm development, making it possible to estimate the pH at the metallic surface. The biocorrosion model is based on strain driven dissolution. The final model iterates between biofilm development that changes the pH at the surface and biocorrosion that changes the geometry of the substratum.