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

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