This work presents a semi-empirical corrosion model that is applicable for downhole corrosion predictions with both H2S and CO2. The current model accounts for solution activities and gas fugacities. Furthermore it is based on the popular de Waard-Milliams equation but with new modifications to provide accurate predictions at elevated temperatures and pressures.The new changes to the model provide a dampening effect to prevent overestimation at high temperatures. The model is capable of predicting corrosion rates shear stress and pH values. Results from the model have been compared with both field and laboratory data and shows a strong parallel with these data.Keywords: Downhole applications deWaard-Milliams modelgas fugacities corrosion prediction Semi-empiricalcorrosion model point model