Problems in AC impedance measurements of high resistance system in thin-film electrolytes

AC impedance measurements were carried out on an iron electrode covered with a dilute thin layer electrolyte. Such a system is used to measure corrosion reactions similar to those occurring during atmospheric corrosion of metals. The methods used include three-electrode, two-electrode (potentiostatic and galvanostatic) techniques. Comparison between these methods was made, and attention was paid to the methodological aspects of AC impedance measurements in high resistance systems. The results show that two-electrode systems, i.e. without the interference of a reference electrode, particularly in high resistance systems, generally give better results than three-electrode systems. Moreover, the galvanostatic method, under certain circumstances, is preferred in terms of the stability of the system and the accuracy of the results