A model is proposed that determines the influence of the condensation rate on the Top-of-Line Corrosion (TLC) under dewing conditions. The model is based on an analytical and numerical solution of the flow field in the falling film of the condensate. A numerical solution is then used to compute the mass transfer by convection and diffusion of the dissolved species. At the wall, the boundary conditions are given by empirical equations for the corrosion rate. The numerical solutions are compared with data from the field observations.