Hopf frequency measurement by electrochemical impedance spectroscopy: application to the transpassive dissolution of nickel

The linear stability of the electrochemical system is given by the Nyquist criterion onto the complex impedance plane. This method is well known for a long time, Koper has proposed a new stability criterion derived from the Nyquist one. This application formulate equivalent conditions for detecting bifurcations. When the Nyquist diagram pass through the origin of the complex plane the system will undergo a bifurcation. If the intersection occurs for zero frequency, it is a saddle node, if the frequency is nonzero, it is a Hopf. One application of these criterion is given for the experimental transpassive nickel dissolution.