Detailed modeling of corrosion macrocells on steel reinforcing in concrete

Numerical modeling of the distribution corrosion of steel reinforcing bars (rebars) in concrete structures is complicated by the spatial distribution of the rebars in the volume of concrete, by nonlinear boundary conditions associated with the polarization of the corrosion reactions at the steel surface, and by mass transfer processes of the reactants in the bulk of the concrete. A computational method for solving the governing equations has been developed from finite difference representations and a solution procedure that retains the nonlinear character of the boundary conditions. A strategy was successfully devised to compute the local potential and current density at the rebar surface with a minimum of computational effort. Both the problem of free corrosion and cathodic potential are discussed for the example of a square slab, reinforced with a double mat of crossing rebars. (C) 2001 Elsevier Science Ltd. All rights reserved.