Interpretation of Electrochemical Noise Generated by Multiple Electrodes

To investigate the effects of galvanic coupling between dissimilar materials by electrochemical noise methods, an approach based on the use of an array of electrodes comprising two dissimilar pairs of identical electrodes is proposed. The individual currents flowing through each electrode are measured simultaneously with the potential of the array. For each electrode, the apparent noise resistance, , is determined from the square root of the potential variance divided by the individual current variance. For two dissimilar pairs of identical electrodes and under the assumption that nominally identical electrodes have identical resistance and are equally noisy, may approach closely to the true noise resistance of electrode n or be proportional to R_n. The analysis is facilitated by the introduction of “virtual electrodes,” corresponding to a convenient sub-array of real electrodes, and obtained by mathematical manipulation of the individual currents in the time or frequency domain. By using this approach, the validity of the assumptions on the relative magnitude of the noise sources and electrode resistances that are often necessary to evaluate R_n can be verified partially or completely. For example, the electrochemical noise data recorded from four identical electrodes and from two dissimilar couples of identical electrodes are discussed.