Approach to consider self-corrosion in corrosion monitoring of reinforced concrete structures exposed to chlorides

Corrosion processes of steel in concrete contaminated with chlorides take place as macrocell corrosion as well as self-corrosion (i.e., microcell corrosion). While macrocell corrosion can be detected by element current measurement, self-corrosion cannot be precisely determined electrochemically. This results in deviations in corrosion investigations between the mass losses calculated coulometrically from macrocell current measurements and the actual, corrosion-related gravimetric mass losses. This is relevant in practice as part of corrosion monitoring. In the following, a simple approach is presented by considering this self-corrosion current mathematically in the macrocell current measurement. The empirical regression functions determined for this purpose can be applied to a large number of different influencing parameters and allow the determination of the cumulative steel degradation at time-varying macrocell current densities under consideration of different safety levels. This allows a much more accurate estimation of the actual corrosion-induced mass losses during corrosion monitoring than previously possible. Self-corrosion results in deviations between the electrochemically calculated mass losses of the reinforcement from the macrocell current measurement and the actual gravimetric mass losses during corrosion monitoring in chloride-contaminated reinforced concrete structures. Empirical regression functions are presented that can be used to take self-corrosion into account with various confidence levels.image