Investigation on the corrosion behavior of aluminum alloys 3A21 and 7A09 in chloride aqueous solution

•3A21 alloy had good corrosion resistance due to its uniform and fine microstructure.•The serious pitting corrosion of 7A09 was owing to its microstructural heterogeneity.•The anodic activity of the intermetallics of 7A09 ceased after immersion for 4 days.The corrosion products were mainly composed of Al2O3, Al(OH)3 and AlCl3.

The corrosion behavior of aluminum alloys 3A21 and 7A09 in 3.5%NaCl solution were studied by using microstructure examination, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform-infrared (FT-IR) spectroscopy. Results show that the two kinds of alloys both suffer from pitting corrosion and the corrosion of 7A09 is much more serious than that of 3A21. The EIS tests reveal high corrosion rate for 7A09 alloy and good corrosion resistance for 3A21 alloy. XPS and FT-IR analysis demonstrate that the corrosion products are mainly composed of Al2O3, Al(OH)3 and AlCl3.