A Revised Model for Electrochemical Frequency Modulation for Corrosion Estimation

Abstract

Electrochemical frequency modulation technique allows for evaluation of corrosion rate without prior information of the Tafel parameters. The basic premise of this approach is that since the material degradation can be described by a nonlinear model, the application of an AC perturbation signal will result in the generation of higher harmonics corresponding to the multiples of the original signal frequency. However, the previous research has ignored the following: (i) the effect of the double layer capacitance (Cd) at the surface of the corroding electrode, and (ii) the solution resistance (Rs) on the output signal, which makes the estimation of faradaic current impossible. Thus, the true corrosion rate cannot be calculated.Our research has shown that when these two effects are taken into account, the output signal displays shift in the higher order harmonics, which is a function of not only the order of the harmonics but also of the Tafel parameters Cd, and Rs. Thus, it becomes possible to calculate the faradaic current and accurately estimate the corrosion rate.