OSCILLATORY BEHAVIOR AS ELECTROCHEMICAL FLUCTUATIONS DURING THE TRANSPASSIVE ELECTRODISSOLUTION OF COPPER IN PHOSPHORIC ACID

Abstract

Transpassive electrodissolution of copper in phosphoric acid was studied froma dynamical point of view. A new electrochemical oscillation named corrosion oscillation as the form of electrochemical noise appears at the corrosion region. The pre-passivated copper electrode in phosphoric acid media shows a fluctuated current within the active potential region. The current oscillation in this system, and generally in electrochemical systems, is sensitive to the initial condition of the electrode surface from heterogeneity point of view. We show that the noise in the current-potential curve is caused by a tiny instability of the passive film, a transition from the passive to extrapassive states and vice versa. Here we demonstrate that the current oscillations can also be observed in the low scale of electrochemical noise. Moreover, the possible mechanism for the electrochemical noise and generally the other noises are also described. The study is of interest from an interdisciplinary point of view as shown by complicated processes such as noises, can be recognized in a dynamical system by applying a closer view in a lower scale. Thus, it is a typical (but not general) study for investigation and monitoring tiny processes in scale, whereas they are so complicated.