Development of anodic coating on aluminum by Na2Cr2O7/H2SO4 anodizing

In this study, anodic oxidation of aluminium was performed in aqueous solution containing both sodium dichromate and sulphuric acid, on aluminium anode, by electrolysis. Anodizing protect the aluminum by making the surface much harder than natural aluminum. Aluminum oxide is grown out of the surface during anodizing and then becomes aluminum hydrate that is extremely hard. The study work 0,4 M H2SO4 + 3,96 g/100 ml Na2Cr2O7 at solution and different potentials (0, 3, 6 ve 9 V) performed at different anodizing times (300, 600 ve 900 second) on aluminium. For the appropriate corrosion performance investigated, the corrosion potentials (Ecor) and the inverse polarization resistance (Rp) are determined. Also electrochemical impedance spectroscopy was used. These results showed that the oxide coating (Al2O3) obtained on aluminum surface exhibited important corrosion protection.