The double-side friction stir welding is used for a 42 mm thick 6082-T6 aluminum alloy. The intergranular corrosion behavior of joints delamination specimen is studied by intergranular corrosion test. Based on the microstructure,microhardness and precipitate characteristics of the joint,the key factors affecting the intergranular corrosion behavior of the joint microdomain are analyzed. The results show that the weld nugget zones of the top and bottom layers are small equiaxed crystal structures,and under the action of double stir,the grains of the lapped weld nugget zone are finer. The microhardness distributions of the surface layer and the middle layer of the joint are W-shaped and V-shaped,respectively,and the corrosion degree of the joint does not correspond to the microhardness. Serious intergranular corrosion occurs in the base metal and HAZ2 of each layer of the joint,while no obvious intergranular corrosion is observed in other microdomains. The potential difference between the precipitates and the precipitate free zone in the base material zone and the Cu-rich phase particles on the grain boundary of the HAZ2 zone are the main reasons for the high sensitivity of the intergranular corrosion.