| Concepts of nonlinear dynamics are applied to the kinetics of electrochemical corrosion. The theoretical part of the research includes, review of the fundamental concepts of chaotic dynamics, analysis of an existing model for chemical corrosion, and development of a new model for electrochemical corrosion by combining two existing models. This new model is characterized by three state variables and five control parameters. Evaluation of the nonlinear dynamics exhibited by this model for a limited region in parameter space revealed the existence of spontaneous chaos.; Experimental part of the research resulted in the discovery of a new electrochemical system, which under appropriate parameter conditions, exhibits periodic and low dimensional chaotic behavior. X-ray diffraction and SEM techniques were used to identify the passivating films formed on the surface of the rotating copper anode. The concepts of nonlinear dynamics are applied to the timeseries from the experiments, to diagnose and quantify the chaotic behavior exhibited by the experimental system. This includes, construction of return maps, reconstruction of chaotic attractors in the embedding phase space using time delay coordinates, and calculation of the largest Lyapunov exponent. Existence of mixed mode oscillations was found in the system by scanning a control parameter (rotation rate).; The concept of controlling chaos which enables one to convert the chaotic behavior of a system to a periodic response is also investigated. A new recursive proportional feedback (RPF) control strategy was developed which in addition to being more powerful than the existing control techniques, is easily applicable to experimental situations. This new RPF control strategy was then used to control chaos both in the model for electrochemical corrosion, and the experimental electrochemical system. |
