On the corrosion rate measurement of reinforcing steel in chloride induced macrocell corrosion

Abstract

This study investigates the corrosion rate measurement of reinforcing steel under chloride-induced macrocell corrosion in reinforced concrete (RC). The corrosion rates of RC columns with different cover thicknesses and chloride concentrations were evaluated using different techniques and cathode over anode ratios. The applicability of the Stern-Geary equation on the macrocell corrosion of RC was studied. The results show that the corrosion rate of highly corroding steel can be underestimated by an order of magnitude by the linear polarisation resistance method due to a failure to compensate for diffusion resistance. The effect of macrocell corrosion on the measurement of polarisation resistance is moderate with a relative error less than 2. The galvanostatic polarisation technique can eliminate the influence of diffusion resistance and therefore reliably measure polarisation resistance. A B value of 52 mV is recommended under macrocell corrosion.