Enhanced Growth Rate of Anodized Film on Al with Addition of Ethylene Glycol

The additive organic substance has been used in the anodizing electrolyte to improve the growth rate and characteristics of the oxide film formed by hard anodizing technique. The effect of additive ethylene glycol (EG) on the growth rate of the hard anodic film is investigated in this work by recording the voltage-time curves, observing the surface appearance, and measuring the film thickness. Anodizing was carried out at a constant current of 300 A m^-2 in 2 M H2SO4 solution at 10°C. The anodizing process was terminated at 30, 45, and 60 min. The additive EG was introduced in the electrolyte with concentrations 0, 10, 20, and 30%. The results indicates that addition of EG enhances the electrochemical reaction rates occurred on the Al metal surface as demonstrated by the increase of slopes from 0.1 V/min to 0.6 V/min with increasing EG concentration in the voltage-time curves. The acceleration of the reaction rates contributes to the increase of the film thickness ranging from 30-56 μm. Meanwhile, in the absence of EG, the voltage output is relatively constant at 20 V and the film thickness (26 - 43 μm) is controlled by the anodizing time.