An equivalent electrical circuit has been tentatively formulated in order to simulate the macrocell corrosion behaviour of concrete rebars placed in parallel. The measurements have been made on mortar specimens by means of EIS. The results have been obtained from every electrode at their open circuit potential and from the two electrodes connected (macrocell formation). Since this procedure is not completely correct, an improvement has been attempted by polarizing both rebars to the macrocell potential. The addition in parallel of these data has been compared to the data for the macrocell couple, finding an almost perfect fitting.