Potential Scanning Impedance Spectroscopy to Investigate Dissolution Mechanisms of Iron

Electrochemical impedance spectroscopy (EIS) is powerful method to analyze dissolution mechanisms of metals because time constants for elementary reaction steps and formation of reaction intermediate can be discriminated. Impedance spectrum is generally measured by using frequency response analyzer whose principle is on the basis of Fourier transformations of sinusoidal input and output signals. In the present paper, we employ a wavelet transformation to determine impedance spectra of dissolving iron electrode because the wavelet transformation gives the power spectrum densities with recording the time and the time variation of the spectra can be discussed. We used complex Morlet mother  wavelet in order to obtain the complex number data in the frequency domain. The time-dependent impedance of the dissolving iron electrode can be determined by calculating cross spectra of the wavelet coefficients of current and potential signals. We developed potential scanning impedance spectroscopy (PSIS) using the impedance determination by wavelet transformation. By PSIS, we can obtain the successive impedance spectra with measuring the potentiodynamic polarization curve of metal electrode simultaneously, and discuss the dissolution mechanisms of iron in aqueous solutions.