New Spectro-Electrochemical Setup for Determining the Rate Change of Oxide Film Growth of Aluminum by White Light-Optical Interferometry
White light interferometry was applied to obtain the rate change of an oxide film growth of aluminum samples during the anodization in aqueous solutions. The thickness (d) of the oxide film was determined by Fabry-Perot, i.e., white light, interferometry. In other words, for the first time, an electromagnetic, i.e., Fabry-Perot, method was utilized to obtain the rate change of the oxide film growth of aluminum samples rather than the electronic, i.e., direct current (DC) or alternating current (AC), methods, as a function of the time (t) of the anodization processes. Therefore, the abrupt rate change of the d(d)/dt was called anodization-emission spectroscopy. The anodization process of the aluminum samples was carried out by the DC method in different sulphuric acid concentrations (0.0,2,4,6,8,10% H2SO4) at room temperature. In the meantime, the Fabry-Perot interferometry was used to determine the difference between d of two subsequent values, d(d), as a function of the elapsed time, dt, of the DC experiment for the aluminum samples in H2SO4 solutions. The Fabry-Perot interferometry was based on a fiber-optic sensor to make real time-white light interferometry possible at the aluminum surfaces in the acid solutions. Also, an abrupt rate change of the d(d)/dt of the oxide film of the aluminum in 2.0,4.0,6.0,8.8,10.0% H2SO4 and in deionized water (0.0% H2SO4) was observed to occur once between 10 to 20 minutes. Then, the d(d)/dt of the oxide film was recorded around zero between 20 to 30 minutes. Eventually, the d(d)/dt of the oxide film was gradually increased during the remaining elapsed time of the experiment.
