A model is presented for the prediction of the corrosion rate by CO2 under dewing conditions. A mechanistic approach is developed that takes into consideration the hydrodynamics, thermodynamics, heat and mass transfer, chemistry, and electrochemistry during the phenomenon of Top-Of-The Line corrosion. This model is validated by experimental data. It offers a better insight on the role played by primary parameters such as the temperature, the total pressure, the partial pressure of CO2, the gas velocity, and the condensation rate.