In the present inve stigation, 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 % H2SO4) 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 AC impedance and double layer capacitance of aluminium samples by holographic
interferometry during anodization processes in aqueous solution. Consequently, holographic interferometry
was 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 AC 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.