Measurement of the electrical resistance of aluminium samples in sulphuric acid solutions by optical interferometry techniques

Holographic interferometry was utilized for the first time to measure the electrical resistance of aluminium samples during the initial stage of anodization processes in aqueous solution without any physical contact. The anodization process (oxidation) of the aluminium samples was carried out chemically in different sulpheric acid concentrations (0.5 - 3.125% H2SO4) at room temperature. In the mean time, a method of holographic interferometric was used to measure the thickness of anodization (oxide film) of the aluminium samples in aqueous solutions. A long with the holographic measurement, a mathematical model was derived in order to correlate the electrical resistance of the aluminium samples in solutions to the thickness of the oxide film of the aluminium samples which forms due to the chemical oxidation. In addition, a comparison was made between the electrical resistance values obtained from the holographic interferometry measurements and from measurements of electrochemical impedance spectroscopy. The comparison indicates that there is good agreement between the data from both techniques, especially when an electromagnetic coefficient was introduced to make the values of the electrical resistance from both techniques are nearly the same.