ON THE CURRENT-DENSITY REQUIRED TO PROTECT STEEL IN ATMOSPHERICALLY EXPOSED CONCRETE STRUCTURES

Mixed potential theory suggests that the current required to cathodically protect steel in atmospherically exposed concrete is strongly dependent on the corrosion rate. At modest corrosion rates, typical design current densities would not achieve the level of cathodic polarisation required by commonly accepted protection criteria. However a cathodic current effectively lowers the unprotected corrosion rate by removing chloride ions and increasing the pH at the cathode. This work suggests that the prevention of further corrosion and the achievement of an adequate level of polarisation by a cathodic protection system is strongly dependent on these protective effects.