Electrochemical Noise - Simultaneous Monitoring of Potential and Current Noise Signals from Corroding Electrodes

Abstract

Abstract Electrochemical noise is a generic term used to describe the spontaneous fluctuations of potential or current which occur at an electrode interface. The stochastic processes giving rise to the noise signals are related to the electrode kinetics, and in the case of a corroding system, may be related to the corrosion rate and mechanism. Analysis of the current and potential noise, around the free corrosion potentials, is shown to be a sensitive monitoring method. Problems associated with monitoring current noise on a freely corroding electrode may be overcome by coupling nominally identical electrodes via a low noise zero resistance ammeter. The variation in both current and potential of the electrodes may be simply monitored using analogue instrumentation, or (in order to facilitate more detailed analysis) digital techniques. Examples of the application of the technique are presented for a variety of situations, and some consideration is given to the theoretical aspects concerning the origin of the noise signals in electrochemical systems. The current fluctuations may be related to corrosion current and rate information may be derived. Furthermore, the use of current and potential noise techniques in tandem facilitates the interpretation of the mechanism and rate of attack and also allows direct comparison of data with that obtained from more conventional electrochemical techniques (e.g. linear polarisation resistance and ac impedance).