A Quantitative Study of Concrete-Embedded Steel Corrosion Using Potentiostatic Pulses

The corrosion rate of steel in reinforced concrete structures may be estimated from the potential decay curve after a pulse interruption, provided that the steel surface area intervening in the measurements is known. Considering that the time constant (τ) of the corrosion process is independent of the surface area, it is also possible to determine the corrosion rate from direct measurements of τ without the need to know the rebar surface area, provided that the double-layer capacitance value is previously known or a reasonable value of this variable is assumed. The method may also be applied in real-sized structures, using small, easy-to-use counter electrodes. Experiments have been performed using small mortar specimens (8.0 cm by 5.5 cm by 2.0 cm) and larger-sized slabs (90 cm by 65 cm by 10 cm) simulating real structures. Rebars were embedded in concrete with and without additives (chlorides and nitrites) and with a cement/sand/water ratio of 1/3/0.5. The reliability of the data obtained is comparable to that of generally accepted conventional electrochemical procedures for measuring linear polarization resistance.