The transient response to a current pulse applied to steel reinforcement bars in concrete has been analyzed by means of a new computational algorithm based on discretised approximation of the fractional difference operator. An optimization strategy has been designed to obtain a set of optimal values for the characteristic corrosion parameters from the information contained in the potential-time transient (specially, in the decaying part of the trace). The method compares the experimental response with the simulated response in the time domain obtained from an electrical circuit model which includes the effects of a constant- phase element and diffusion coupled with charge transfer. The practical possibilities of this method for extracting corrosion parameters (in particular, the charge-transfer resistance) have been demonstrated with steel reinforcements embedded in concrete in the presence and absence of chloride additions. (C) 2004 The Electrochemical Society.