Electrochemical impedance spectroscopy of anodic processes on Co2Si electrode in sulfuric acid solutions

Frequency dependences of the impedance of Co2Si electrode in 0.5 M H2SO4 and 0.05 M H2SO4 + 0.45 M Na2SO4 solutions are measured in the ranges of the active dissolution, active-passive transition, passive state, and transpassivity. There are potential values in the active range when the impedance can be interpreted as the impedance of the selective cobalt dissolution. The impedance spectra in the passive range and in the beginning of the transpassive potential range are described with the use of an equivalent circuit taking into account the existence of an oxide layer on the electrode surface.