Electrochemical impedance spectroscopy in the presence of non-linear distortions and non-stationary behaviour: Part II. Application to crystallographic pitting corrosion of aluminium

The framework about the odd random phase multisine with a random harmonic grid [E. Van Gheem, R. Pintelon, J. Vereecken, J. Schoukens, A. Hubin, P. Verboven, O. Blajiev, Electrochim. Acta, submitted for publication] developed in Part I of this series of two papers, is now applied to aluminium (99.5 wt.%) in an aerated 0.5 M NaCl solution. Due to the special design of this excitation signal it becomes possible to obtain information about the non-stationary behaviour of the aluminium system within successive measurements, and to correct the impedance spectra for this behaviour. In addition, the proposed methodology determines the type and level of non-linearities in the measured spectra. From these results the investigator has two choices. On the one hand, optimal EIS measurement conditions for linear modelling purposes can be derived, based on a tradeoff between the minimization of the level of the non-linearities and an acceptable noise level. On the other hand, from the results with the best signal to noise ratio, the knowledge about the non-linear distortions in the impedance spectra can be further elaborated as a useful tool during the modelling procedure. Finally, the standard deviations of the corrected impedance spectra are calculated, which are generally used as a weighting factor to improve the modelling procedure.