During the extraction of chlorides from concrete there occur processes involving transfer of mass and electric charge via pore solution components. On the basis of the relations which exist between the concentrations of these components, the electric field intensity, the temperature, and the mechanical stress, thermomechanics equations of a multicomponent medium have been used for analytical description. On the basis of equations for the balance of mass, electric charge, momentum, energy and entropy inequality, equations of ion flows have been determined, which are justified in the general effect of the electric field action on the concrete covering. The occurrence of processes which are recognised as dominant ones during the chloride extraction has allowed us to significantly simplify the equations and reduce them to formulas permitting a practical use. By approximating the electrochemical potentials of the leading ions via the linear function of concentration and electric field potential, a flow equation has been determined which has a shape similar to the classical diffusion equation. In order to define the electrodiffusion coefficient occurring in this equation an inverse problem has been formulated and then numerical values of this coefficient have been evaluated using the results of experimental tests.