Influence of catholytes on the generation of steel corrosion in concrete with accelerated chloride migration method

In the aim of developing localized corrosion, artificial corrosion on a steel sheet coated with concrete was implemented through accelerated chloride migration with a constant applied voltage (20 V). Four chloride solutions (20 g/L NaCl) with different initial pH were used. The pH values and chloride concentrations of the solutions were recorded during the test. Electrochemical non-destructive measurements of corrosion potential (Ecorr) and apparent linear polarization resistance (Rp,app) of the steel sheet were made. The concrete cover was then removed to observe corrosion visually (autopsy). The corrosion products were characterized by XRD and SEM and the results showed that the migration of chloride ions in concrete was slowed down by hydroxide ions, which was highlighted by a reduction of chloride transport number. Whether chloride ions were present at the steel interface or not, corrosion occurred because of acidification at the steel sheet/concrete interface due to the anodic polarization. However, when chloride ions were present, the corrosion propagation phase started earlier and the corrosion rate was higher.