Influence of the space-charge region on electrochemical impedance measurements on passive oxide films on titanium

Both potentiostatically and galvanostatically controlled electrochemical im pedance spectroscopy were used to show that the impedance obtained from pas sivated titanium electrodes is dominated by the capacitance of the space-ch arge layer. As a result neither the thickness of the oxide layer nor its ra te of thinning can be readily determined from impedance measurements. Furth ermore, it appears that the corrosion rates of passive metals determined by EIS may significantly overestimate the true rate of dissolution. No signif icant differences were observed between the impedance data obtained from th e galvanostatic acid the potentiostatic measurements. (C) 2000 Elsevier Sci ence Ltd. All rights reserved.