Corrosion rate of steel in concrete - From laboratory to reinforced structures

Measuring corrosion rate of rebars in reinforced concrete is essential for establishing service life prediction of structures and controlling the efficiancy of repair methods. Different electrochemical techniques, all based on measuring the polarization resistance, are used in the laboratory and on site, In calculating corrosion rate from the experimentally determined Rp value, two main problems arise: current distribution between the small counter elelctrode and the rebars on real structures and localized corrosion attacks. In this work results from laboratory experiments on macrocell corrosion are presented, showing the influence of resistivity and geometrical arrangement on the macrocell corrosion rate under open circuit conditions and under an external anodic pulse. From the results it can be concluded that the polrization resistance measured experimentally corresponds to the corrosion rate of the anode in the macrocell, Most of the imposed current is flowing to the local anode and thus signal confinement for local corrosion attacks is not necessary. The segmented counter electrode opens a way to determined localized corrosion rates.