Applying the electrochemical microcell in copper corrosion studies: Local electrochemical impedance spectroscopy measurements

Abstract

The corrosion behaviour of copper expose to chloride environment has been studied by Local Electrochemicallmpedance Spectroscopy (LEIS)performed with the electrochemical microcell. The development of such a set-up has been crucial task since we shown that the electrode positioning inside the micocell influence the LEISresponse. However, this technique is well suited for corrosion studies since it allows delimitating small areas (depending on the capillary size) on which the study is performed. A three-electrode electrochemical system was used for the LEISmeasurements. Both the reference electrode (a silver wire covered by a silver chloride) and the counter-electrode (a platinum wire) were located inside the microcell, with the later passing through the capillary. The copper surface was delimitated by the diameter of the capillary using a silicon rubber. The electrolyte was filling the microcel! and the capillary with a micro syrinqe, The influence of electrochemical microcell geometry on the LEISmeasurements was evaluated to assure a good understanding and a complete description of the electrode response. Both the influence of the microcapillary diameter and of the counter-electrode position inside the capillary was investiqated. A linear diffusion through a finite diffusion layer was evidenced by LEIScarried out with the electrochemical microcell. The effect of the edges on the diffusion processes could not be identified even though the small size of the exposed area. The thickness of the diffusion layer seems to be affected by the distance between the counter and the working electrodes. -