Optical interferometry techniques was used for the first time to measure the surface
resistivity/conductivity of anodized aluminium samples in aqueous solution without any physical
contact. The anodization process (oxidation) of the aluminium samples was carried out in
different sulphuric acid solutions (1.0-2.5 % H2SO4), by the technique of electrochemical
impedance spectroscopy (EIS), at room temperature. In the mean time, the real-time holographic
interferometric was carried out to measure the thickness of anodized (oxide) film of the
aluminium samples during the anodization processes. Then, the alternating current (AC)
impedance (resistance) of the anodized aluminium samples was determined by the technique of
electrochemical impedance spectroscopy (EIS) in different sulphuric acid solutions (1.0-2.5 % H2SO4) at room temperature. In addition, a mathematical model was derived in order to correlate between the AC impedance (resistance) and to the surface (orthogonal) displacement of
the samples in solutions. In other words, a proportionality constant (surface resistivity or
conductivity=1/ surface resistivity) between the determined AC impedance (by EIS technique)
and the orthogonal displacement (by the optical interferometry techniques) was obtained.
Consequently the surface resistivity (ρ) and conductivity (σ) of the aluminum samples in solutions were obtained. Also, electrical resistivity values (ρ) from other source were used for comparison sake with the calculated values of this investigation. This study revealed that the measured value of the resistivity for the anodized aluminium samples were 2.8×109, 7×1012, 2.5×1013, and 1.4 ×1012 Ohms-cm in 1.0%,1.5%, 2.0%, and 2.5 % H2SO4 solutions, respectively. In fact, the determined value range of the resistivity is in a good agreement with the one found in literature for the aluminium oxide ,85% Al2O3 (5×1010 Ohms-cm in air at temperature 30C°), 96% Al2O3 (1×1014 Ohms-cm in air at temperature 30C°), and 99.7% Al2O3 (>1×1014 Ohmscm in air at temperature 30C°).