The Electrochemical Reaction Of The Paa Oxide Film

To explore the electrochemical reactions in the process of the porous anodic aluminum (PAA) formation, the anodizing processes of aluminum and chemical composition were researched in four acid electrolytes. The anodizing processes as well as the surface and cross-section morphologies were characterized by means of the voltage-time (V-t) curves test system, the field emission scanning electron microscopy, the energy dispersive X-ray apparatus, the UV spectrophotometer, the Fourier transform infrared spectroscopy and the X-ray diffraction. The electrochemical reactions and the formation mechanism of PAA were analyzed.In this paper, the differences and disciplinarian of anodizing V-t curves were compared in four acid electrolytes. According to the morphologies of PAA and the analysis of chemical composition, we discussed the ion mobility and feasible electrochemical reactions during the PAA formation process. Oxygen evolution is ascribed to anionic discharges as the oxide growing to a certain stage. Subsequently, we put forward to oxygen bubble mould effect (OBME) which results in the formation of regular nanopores. And it can be proved by comparing the oxide films anodized in several above mentioned electrolytes which were added suitable anionic reducer. To exclude the effect of oxygen from air, two anodizing processes under open and closed conditions were analysed. A series of experiments in various pressures were carried out to futher demonstrate the OBME. In the end, we modified the theory of acidic electricfield-assisted dissolution and proposed a new growth model for PAA as well as feasible electrochmical reactions.