Electrochemical impedance measurements have been carried out in micro-sized systems for studying the corrosion of copper in chloride-containing environment. Two different configurations, with different delimitated small exposed areas, have been considered: copper microelectrodes and microcapillaries into an electrochemical microcell. The influence of the size for each configuration has been studied. The comparison of both measurements has also been carried out in order to investigate the effect of the electrodes configuration on the mass transport processes. It was shown that the diffusional response is sensitive to the cell configuration.