Revisiting the analysis of impedance data for double layer capacitance.

A method was developed to extract double layer capacitance (C(dl)) from data displaying time constant dispersion at a frequency where the phase angle reached its maximum (f1). This method was implemented in a set of synthetic data and the Kramers-Kronig (K-K) transformable experimental data for mild steel in an acidic solution. The double layer capacitance values were compared with ones extracted from the constant phase element (CPE) parameters, Y(o) and α, at a frequency where the imaginary part of the impedance reached its maximum (f2). A significant closeness of the results was reached for two different frequencies.