Effect of anodizing and nano silica top coat on corrosion protection of recycled aluminum substrate

Natural aluminum oxide is unstable in corrosive environments. The aluminum alloys need a protective coating to resist against corrosion attacks. Sol-gel derived films can be deposited on metals to improve their resistance to oxidation and corrosion. However, only few reports have been published on low adhesion of sol-gel coatings on metals and more specific investigations are necessary to define the limits of sol-gel applicability in this field. The anodizing pretreatment is commonly applied to enhance the adhesion and corrosion protection of the aluminum alloys. Porous structure is formed because of the aluminum alloy impurities and the difference in the oxide growth at the metal surface during the anodizing process. In this study potentio-dynamic polarization curves have been used to investigate the effect of anodizing pretreatment and alcohol-based sol layer on corrosion protection of aluminum. The polarization curves were obtained between -150 mV and +150 mV potential ranges and protection efficiency calculated.