Electrochemical Parameters of Aluminum Oxide Film in Situ During Anodization of Aluminum by White Light-Optical Interferometry

Abstract Both of 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 (H2SO4). 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 (Al2O3) 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 H2SO4 solutions, for 90 minutes. Then, the obtained d of the Al2O3 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 in agreement with those of the DC electrochemical method. In contrast, the calculated J by Fabry-Pérot interferometry was found in a 3 fold discrepancy with data obtained by the EIS.