Investigation on the effectiveness of the repair method 8.3 "Corrosion protection by increasing the electrical resistivity" in chloride‐containing concrete Part 3: The influence on corrosion of chloride‐contaminated concretes under protective coatings

With the implementation of the repair method "increasing the electrical resistivity by coating" (MR 8.3), no direct repassivation of the reinforcing steel is initially intended. The success of the repair is rather linked to the change of the corrosion‐relevant parameters over time. These include an increase in the concrete resistivity due to dehydration and gradual decrease in corrosion currents and driving voltages on the reinforcing steel. Within the scope of a research project funded by the German Research Foundation (DFG), application limits for the repair principle W‐Cl could be defined. The chloride content present in the concrete at the rebar is the significant limiting factor for the application. While the corrosion activity even with moderately dehydrated specimens under diffusion‐retarding coatings at chloride contents of 1 wt% Cl⁻/c is in the range of the passive current density, this cannot be generally determined for chloride contents of 2 wt% Cl⁻/c. The type of coating has a decisive influence on the dehydration of the concrete. For example, less dense concretes under a permeable coating (acrylic dispersion/OS 4) can dry out to such an extent that the passive current density is reached. With semipermeable coatings and the presence of high chloride contents of 2 wt% Cl⁻/c, the repair principle W‐Cl does not lead to success according to the available test results.