Recycling Al alloys promotes greater sustainability, as the energy required to produce recycled alloys is only about 5 % of that needed to produce the same amount of primary alloys. However, the build-up of impurities, such as Zn, during the recycling process can negatively affect the corrosion resistance of recycled alloys. The results show that the susceptibility to intergranular corrosion increased with minor additions of zinc (≤ 0.06 wt%). Zn was found to segregate along the grain boundaries, and the STEM-EDS results indicate that the Zn incorporates into the structure of Mg-Si containing grain boundary precipitates.

Al-Mg-Si alloys are known as structural materials and are primary alloys in the automotive industry to achieve weight reduction. Shifting toward sustainability, lower energy consumption, and less CO2 emission necessitates recycling. However, the unavoidable accumulation of scrap-related impurities, e.g., Cu and Zn, during the recycling process can influence corrosion resistance of recycled alloys. The results show that Al-Mg-Si alloys containing 0.05 wt% Cu exhibit low intergranular corrosion resistance. The intergranular corrosion resistance of these alloys is notably improved by adding 0.06 wt% Zn. Low concentrations of Cu and Zn are found to strongly affect the crystal structure of hardening precipitates.