<title>AC impedance-emission spectroscopy of determining the electrochemical behavior of anodized aluminum in aqueous solutions</title>

Abstract

In the present investigation, holographic interferometry was utilized for the first time to determine the rate change of the alternating current (A.C.) impedance of aluminium samples during the initial stage of anodization processes in aqueous solution without any physical contact. In fact, because the A.C impedance values in this investigation, were obtained by holographic interferometry, electromagnetic method rather than electronic method, the abrupt rate change of the A.C impedance was called A.C impedance-emission spectroscopy. The anodization process (oxidation) of the aluminium samples was carried out chemically in different sulphuric acid concentrations (0.5-3.125 % H2SO4) at room temperature. In the mean time, the real-time holographic interferometry was used to determine the difference of the A.C.impedance of two subsequent values, dZ , as a function of the elapsed time of the experiment for the aluminium samples in 0. 5%, 1.0%, 1.5%, and 3.125% H2SO4 solutions. The A.C impedance-emission spectra of the present investigation represent a detail picture of not only the rate change of the A.C.impedance throughout the anodization processes , but also, the spectra represent the rate change of the growth of the oxide films on the aluminium samples in different solutions. Consequently, holographic interferometric is found very useful for surface finish industries especially for monitoring the early stage of anodization processes of metals , in which the rate change of A.C. impedance of the aluminium samples can be determined in situ .