The Role of Mg2Si in the Corrosion Behavior of Al-Si-Mg Alloys for Pressureless Infiltration

The role of Mg2Si in the electrochemical behavior of Al-Si-Mg aluminum alloys has been studied using four experimental aluminum alloys with variations in the Si/Mg molar ratio (A1-0.12, A2-0.49, A3-0.89, A4-1.05), in neutral aerated 0.1M NaCl solutions. Accordingly, the corrosion potential in open circuit (Eoc) and polarization resistance (Rp) were measured. Results show that the augment in Si/Mg molar ratio increases the presence of Mg2Si intermetallic phase. During immersion tests in neutral aerated chloride solutions the anodic activity of the Mg2Si intermetallic decreased rapidly, as indicated by a fast ennoblement of open circuit potential. After the immersion period (7 days), higher Rp values for alloys A3 and A4 (21 and 26 K cm 2 , respectively) as compared to those for alloys A1 and A2 (5 and 10 K cm 2 , respectively), suggest a greater corrosion resistance in Cl containing environments for alloys A3 and A4.