Electrochemical parameters of aluminum oxide film in situ during anodization of aluminum by white light-optical interferometry

Both Fabry–Pérot interferometry and the DC electrochemical method have been simultaneously used for the first time to measure in situ the anodic current density ( J ) of aluminum oxide films in 0, 2, 4, 5, 6, 8 and 10% sulfuric acid solutions (H 2 SO 4 ). The calculated values of J by Fabry–Pérot interferometry were verified by the DC electrochemical method, i.e., a potentiostat, and the AC electrochemical method, i.e., a potentiostat with an accessory of AC impedance spectroscopy (EIS). The corresponding thickness ( d ) of the aluminum oxide (Al 2 O 3 ) film to the anodic current density was determined by Fabry–Pérot interferometry under a potentiostatic condition of 9 V with respect to the open circuit potential of the aluminum samples in the H 2 SO 4 solutions, for 90 min. Then, the obtained d of the Al 2 O 3 films by Fabry–Pérot interferometry was verified by scanning electron microscopy (SEM) and compared to d values that were obtained by the EIS. The calculated J by Fabry–Pérot interferometry was found to be in agreement with those of the DC electrochemical method. In contrast, the calculated J by Fabry–Pérot interferometry was found to have a threefold discrepancy with data obtained by the EIS.