ELECTROCHEMICAL VERSUS OPTICAL TECHNIQUES DURING ANODIZATION OF ALUMINIUM ALLOYS

摘要

In the present investigation, holographic interferometry was utilized for the first time to measure in situ the thickness of the oxide film, Alternating Current (A.C.) impedance, and double layer capacitance of aluminium samples during anodization processes in aqueous solution without any physical contact. The anodization process (oxidation) of the aluminium samples was carried out by the Electrochemical Impedance Spectroscopy (EIS), in different concentrations of sulphuric acid (1.0-2.5 % H_2SO_4) at room temperature. In the mean time, the real-time holographic interferometry was used to measure the thickness of anodized (oxide) film of the aluminium samples in aqueous solutions. Also, mathematical models were applied to measure the (A.C.) impedance, and double layer capacitance of aluminium samples by holographic interferometry, during anodization processes in aqueous solution. 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 thickness of the anodized film, the A.C. impedance, and the double layer capacitance of the aluminium samples can be determined in situ. In addition, a comparison was made between the electrochemical values obtained from the holographic interferometry measurements and from measurements of (EIS). The comparison indicates that there is good agreement between the data from both techniques.