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.