Enhancing aluminum corrosion resistance by two-step anodizing process

Two-step anodizing process can be seen as an effective way to form an adhesive and continued layer on aluminum to enhance its corrosion resistance. Anodic alumina was produced by two types of anodization process, namely single-step and two-step anodizing. We have then evaluated their protection effectiveness against aluminum corrosion in aggressive medium (NaCl 3%). In both cases, X-ray diffraction reveals an amorphous nature of porous oxide films. The electrochemical impedance spectroscopy (EIS) results revealed a strong correlation between the corrosion performance and the morphology of the development anodic films. Also, these results indicated that the morphology and the corrosion resistance of anodic film formed by two-step anodizing process are very improved if compared to single one.