In this study, aluminum was anodized in 0.4 M H2SO4 + 0.145 M H3BO3 solution by means of potentiostatic method. In first step, the most appropriate conditions (anodizing voltage and period) were determined. The voltage-current behavior was investigated between 0 to 30 V and oxide formation potential (15 V) was determined. Then chorono-amperometric measurement was obtained at this potential during 2 hours. Therefore, anodizing process was applied at 15 V between aluminium anode and mild steel cathode. In the second step, the corrosion performance of non-anodized (Al) and anodized samples (Al2O3) have been investigated in 3.5% NaCl solution by using electrochemical impedance spectroscopy and polarization techniques. The interface between metal and solution was modeled with the equivalent circuit successfully. The circuit's elements were calculated with Ivium Soft fitting program. The polarization curves were obtained between -1.8 V and 0.5 V potential ranges. The experimental results proved that the thickness and quality of oxide film was improved with help of anodizing process. Thus the corrosion resistance of anodized aluminum is significantly increased.