Synopsis It is well known and accepted that the presence of chlorides and carbonation of the concrete cover are the two main causes of corrosion of reinforcement, and that the simultaneous occurrence of both chlorides and carbonation is expected to increase the likelihood of corrosion. This likelihood may be quantified and monitored through the use of electrochemical techniques. Polarization resistance and electrochemical impedance measurements on rebars embedded in carbonated mortar containing chlorides have been carried out and the results indicate that these techniques not only allow the extent of corrosion to be estimated but also give information about the effect of the variables on the corrosion process.