Concerning the use of constant phase elements (CPEs) in the analysis of impedance data

Impedance spectra obtained for Al6061 samples that had been anodized and sealed in two different processes and subjected to thermal cycling at three different temperatures have been analyzed using the Equivcrt software using a three-time constant model with four constant phase elements (CPEs). Excellent agreement has been observed between the experimental and the fit data. The high-frequency data have also been analyzed using the ANODAL software. Excellent agreement between the experimental data and the fit data was found in both cases; however, the fit parameters were quite different. The relationship between the CPEs and the surface properties of the anodized samples has been discussed.