Corrosion behaviors of AA5083 and AA6061 in artificial seawater: Effects of Cl-, HSO3- and temperature

Abstract

The electrochemical character of intermetallic inclusions plays a crucial role in the corrosion behaviors of aluminum alloys. The Volta potential of the intermetallic inclusions in AA5083 and AA6061 was investigated. Furthermore, the effects of Cl-, HSO3- and temperature on the corrosion behaviors of AA5083 and AA6061 were studied. The microstructure and composition of the intermetallic inclusion were characterized by scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS). The Volta potential was analyzed by scanning Kelvin probe force microscopy (SKPFM). The alternate immersion test and potentiodynamic polarization curve test were used to evaluate the corrosion resistance. The results show that Al6(Fe, Mn) has a higher potential than that of the AA5083 matrix, resulting in the dissolution of the surrounding matrix. The Mg2Si phase has a lower potential compared to that of the matrix, leading to self-dissolution and dealloying. In addition, the AlFeSi phase has a higher potential and the Mg2Si phase has a lower potential than that of the AA6061 matrix. Pitting corrosion occurs on the surface of both the AA5083 and AA6061 after the alternate immersion test. Increases in the concentration of Cl- and HSO3- accelerates the corrosion of the aluminum alloys. The effect of temperature is affected by both the chemical reactivity and passivation ability. In the same conditions, the AA5083 has superior corrosion resistance to that of the AA6061, which is related to the potential difference between the matrix and intermetallic inclusions.