ABSTRACT
Embedded steel in concrete is normally well protected against corrosion, and this is primarily due to the electrochemical passivation of the steel in the highly alkaline pore solution of the concrete. However, when the passivity of the steel partly or completely breaks down either due to concrete carbonation or presence of chlorides and the corrosion starts, this means that the electrochemical potential of the steel locally becomes more negative and forms anodic areas, while other portions of the steel which have the passive potential intact will act as catchment areas of oxygen and form cathodic areas. If the electrical resistivity of the concrete is also sufficiently low, a complex system of galvanic cell activities develops along the steel. In all of these galvanic cells, a flow of current takes place, the amount of which determines the rate of corrosion. Although the size and geometry of the anodic and cathodic areas in the galvanic cells are also important factors, the rate of corrosion is primarily controlled by the electrical resistivity of the concrete and the availability of oxygen.
