A combination of Fabry-Pérot interferometry and the DC electrochemical method have been used for the first time, in situ, to measure the resistance of aluminium oxide films in 2% sulfuric acid solution. Values of the corresponding resistance of the obtained Al₂O₃ film thickness were determined during anodization of aluminium (Al) in 2% H₂SO₄. The obtained resistance values were verified by electrochemical impedance spectroscopy (EIS) and holographic interferometry. The corresponding resistance (2.4 x10⁹ Ohms) to the final thickness of the aluminum oxide film was found in an agreement with the resistance value that was measured by holographic interferometry, 2.54x10⁹ Ohms, in 2% H₂SO₄. On the contrary, the corresponding resistance (2.4 x10⁹ Ohms) to the final thickness of the aluminum oxide film was found twice the value of the resistance that was measured by the electrochemical impedance spectroscopy (EIS), 1.25x10⁹ Ohms, in 2% H₂SO₄.

Keywords. Aluminium, Thickness of Oxide Film, Fabry-Pérot interferometry, Holographic Interferometry, Electrochemical Impedance Spectroscopy (EIS), Resistance, and Sulfuric Acid.