A numerical simulation of corrosion in a tube is performed with the solution velocity effect taken into account. A two dimensional tube, the cross-section of which is widening or narrowing with increase in distance, is considered. The velocity distribution in the tube is calculated with the Finite Volume Method (Open FOAM), and the derivatives of velocity with respect to the distance from the tube wall is determined at any location of the tube. The corrosion rate of the tube wall is estimated under the assumption that the corrosion rate depends on the velocity gradient, i.e. , it is estimated by solving the Laplace equation under the boundary conditions given with the polarization curves measured under various velocity gradients. The Boundary Element Method (3D-CAFE) is used to solve the Laplace equation. It is shown that the distribution of corrosion rate, including the maximum corrosion rate and its location, is different between the widening and narrowing tubes, even if the average velocities in the two tubes are equal.