Impedance spectroscopy as a technique for studying the spontaneous passivation of metals in electrolytes

Impedance spectroscopy was used to study the initial stage of the spontaneous passivation of a metal immersed in a liquid electrolyte. The error in the measured impedance responses due to the time variability of the passivating system is discussed and evaluated Three models of impedance response during the initial stage of passivation are presented, and are used in the analysis of a Zn/borax solution passive system. The most plausible mechanism of initial passivation in this system involved a time of induction followed by a process of gradual coverage of the metal surface with a passive film. During the process of coverage, the electrical properties of the already covered parts continued to change significantly with time.