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_2SO_4 aqueous solution in the open air and potentiodynamic polarization test in 3.5 wt.%NaCI 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_2SO_4 aqueous solution.The corrosion type of 6063 alloy is pitting corrosion.The Mg_2Si 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 primaryα-AI 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. In this work, a comparison study on the 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.% NaCI 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 the difference of the corrosion progress of these two alloys in 4% H_2SO_4 aqueous solution.The corrosion type of 6063 alloy is pitting corrosion. The Mg_2Si 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-AI and the eutectic, the other is between the eutectic Al and eutectic Si particles. Combine of these tw o 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.