Investigation of corrosion resistance of aluminum anodized by direct and pulse current

Anodizing، as an electrochemical process، has been used for enhancing the corrosion resistance of aluminum and its alloys. The type of current (direct and pulse) strongly affects the properties of anodic films، which are obtained by the anodizing process. In this research، The 1070 aluminum alloy is anodized either by direct current (DC) or by pulse current (PC) (with different frequencies and duty cycles)، in 10%wt acid sulfuric at 10oC temperature. Scanning electron microscopy (SEM) and Potentiodynamic Polarization method (in 0. 5 M NaCl solution)، respectively، are used for characterization of the surface morphology and corrosion resistant of samples، respectively. The results indicate that the pulse current improves the morphology of the anodized samples، but the corrosion resistance of these samples is lower than the sample anodized by direct current. The results also showed that in PC anodizing، Ecorr and icorr of samples are strongly affected by duty cycle. Among the PC samples، the sample is anodized at 200 Hz and duty cycle 70% showed the best corrosion resistance.