Novel fast non-linear electrochemical impedance method for corrosion investigations

The paper presents a novel approach to corrosion rate monitoring using non-linear electrochemical impedance spectroscopy. The authors propose a new variant of non-linear impedance measurement using amplitude-modulated multi-frequency ac perturbation signal. It allows shortening of measurement duration so it is possible to monitor corrosion rate of the systems experiencing rapid changes. In this way a limitation resulting from lack of stationarity condition during the impedance measurements is overcome. Potentialities of the proposed method were presented on the example of carbon steel corrosion in 1 M HCl solution. Sudden changes in the corrosion rate were induced by injection of urotropine as a corrosion inhibitor. The investigations provided time-evolution of charge transfer resistance and corrosion current, clearly reflecting the changes occurring in the investigated system triggered by the inhibitor introduction. Obtained corrosion current values were in a good agreement with the ones acquired using classic method of polarization in the Tafel range.