Corrosion Behavior of Extruded near Eutectic Al–Si–Mg and 6063 Alloys

Abstract

In this work, a comparison study on corrosion behavior of extruded near eutectic Al–12.3%Si–0.26%Mg and 6063 alloys has been carried out by mass loss test in 4% H 2 SO 4 aqueous solution in the open air and potentiodynamic polarization test in 3.5 wt.% NaCl aqueous solution. Results indicate that the corrosion resistance of the near eutectic Al–Si–Mg alloy is less than that of 6063 alloy. Macro/microscopy and scanning electron microscopy results clearly show the difference of the corrosion progress of these two alloys in 4% H 2 SO 4 aqueous solution. The corrosion type of 6063 alloy is pitting corrosion. The Mg 2 Si and AlFeSi particles and surface defects act as nucleation sites for pitting, and the amount and distribution of them have a significant effect on the pitting behavior. For the near eutectic alloy, there are two types of corrosion cells. One is between the extruded primary α-Al and the eutectic, the other is between the eutectic Al and eutectic Si particles. Combination of these two types of corrosion cells leads to a lower corrosion resistance, a higher mass loss of the near eutectic alloy compared with 6063 alloy, and the formation of the paralleling corroded grooves.