Use of Polynomial Approximation in the Electrochemical Frequency Modulation Technique for Determination of Corrosion Rates in Activation-Controlled Systems

Abstract

The electrochemical frequency modulation (EFM) is a promising non-destructive technique that uses a small bi-harmonic disturbance signal along with the discrete Fourier transform (DFT) to calculate the corrosion current and Tafel slopes from a set of equations that rely on harmonic components. Significant results have been published mainly on systems exhibiting Tafel behavior. This work presents the use of polynomial approximation as a data analysis alternative for the EFM technique, which has three main advantages over the procedure proposed by the authors of the EFM technique: a) reduction of the estimation error caused by the capacitance effect, b) reduction of the estimation error caused by high harmonic components and c) the reduction of computational complexity. This analysis was tested experimentally using a traditional three-electrode cell with a carbon steel working electrode and a sodium chloride solution as the electrolyte. Finally, the results were compared to linear polarization tests and weight loss measurements, where a good agreement was found between the proposed analysis and the other techniques.