Influence of Cooling Rate on Intergranular Corrosion in Al-Si7-Mg Alloy

The use of aluminium cast alloys in automotive industry results from a tendency to considerably lower vehicle mass. Subject to working conditions, silumin casts may show occurrence of intergranular corrosion that reduces mechanical properties of the parts produced. The paper presents the influence of cooling rate – R of a plate cast of aluminium alloy EN AC-AlSi7Mg0,3 on the depth of appearance of intergranular corrosion. Samples were exposed to corrosive medium by immersion for 2,5; 12; 24 and 48 hours in an aqueous solution of NaCl+HCl+H₂O. The study demonstrated that cooling rate – R and subsurface porosity significantly influence on distribution and depth of intergranular corrosion in casts of subeutectic silumin.