Transient and gradient analyses of depolarization criteria. Valuable tools in chloride‐induced rebar corrosion monitoring

The aim of this study is to elucidate suitable methods of corrosion monitoring for chloride‐induced rebar corrosion in cracked concrete. Depolarization gradients and transients provide evidence for the electrode kinetics at the steel–concrete interface and the geometry of the macrocell. In the present study, a set of cracked, short‐term chloride‐exposed, reinforced concrete specimens is investigated in terms of their corrosion activity. Primarily, the depolarization behavior was observed by short‐term high‐frequency measurements, allowing for cost‐effective measurement campaigns and robust results. All measurement intervals are split apart via a gradient analysis to enable a congruent, numerical transient analysis. Since the geometry of macrocells in rebar corrosion follows the model of a series of ohmic resistances with a parallel connection of a diffusion‐controlled capacitor and an ohmic resistance, the transient of each depolarization curve with unit time in seconds provides evidence for the present electrode kinetics and macrocell geometry. According to the time, which is consumed until a certain state of depolarization is reached, transient modeling can be used to predict corrosion activity as a function of chloride ingress.