HOPF FREQUENCY-MEASUREMENT BY ELECTROCHEM ICAL IMPEDANCE SPECTROSCOPY- APPLICATION TO THE TRANSPASSIVE DISSOLUTION OF NICKEL

The linear stability of the electrochemical system is given by the Nyq uist criterion onto the complex impedance plane. This method is well k nown for a long time, Koper has proposed a new stability criterion der ived from the Nyquist one. This application formulate equivalent condi tions for detecting bifurcations. When the Nyquist diagram pass throug h the origin of the complex plane the system will undergo a bifurcatio n. 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 c riterion is given for the experimental transpassive nickel dissolution .