Effect of microstructural rearrangement as a result of annealing on the corrosion behavior of 7075 aluminum alloy

Understanding of the relationship between microstructural change and corrosion behavior is essential for achieving the optimum benefit of strengthening precipitates in providing high strength without sacrificing the corrosion resistance of 7000 series aluminum alloys. This work aims at revealing the relationship between the microstructural rearrangement and corrosion behavior of a 7075 series aluminum alloy as a result of annealing at the temperature range of 300 °C–600 °C. Microstructural observation indicated a gradual dissolution of Cu in the solid solution matrix with increasing annealing temperature. At 600 °C, a formation of segregated Al2Cu phase occurred along the grain boundaries. After subjected to corrosion tests, exfoliation corrosion was observed on the as-received specimen, as well as on the specimens annealed at 300, 400 and 500 °C, whilst an intergranular corrosion occurred on that annealed at 600 °C. The corrosion resistance was higher on the specimen annealed at 500 °C compared those annealed at other temperatures, as the result of Cu enrichment the solid solution matrix.