Effect of Cr addition on corrosion resistance of aluminum

In this study, the effect of Cr addition on the corrosion resistance of aluminum was investigated by corrosion test, electrochemical measurements, and elemental analysis on surface of the specimens. The results of the corrosion test showed the mass loss significantly decreased by Cr addition. Furthermore, the corrosion morphology was similar between A1050 and Al-Cr alloy; however, the corrosion depth of the Al-Cr alloy was significantly shallower. Therefore, electrochemical impedance spectroscopy was performed to evaluate the change transfer resistance (Rct) during corrosion test. The Rct of A1050 changed to the lower value; however, Al-Cr alloy maintained the higher value in the corrosive environment. Before the corrosion test, the surface of Al-Cr alloy was covered with the natural oxide film free of Cr, whereas after the corrosion test, the film containing Cr was formed at the corroded site. It was considered that the high corrosion resistance mechanism of Cr addition is due to the high Rct value observed in the corrosion environment, which is attributed to the Cr-containing film formed by corrosion.