Abstract: The intergranular corrosion behavior of friction stir welded 2219 aluminium alloy was investigated. Microstructure, micro-hardness, corrosion morphology and corrosion depth were studied to analyze the difference between BM and WNZ, and intergranular corrosion mechanism of FSW joint was preliminary discussed. The results show that WNZ consists of fine equiaxed grains, and the grain size on top surface is slightly bigger than that on root surface. The highest microhardness is located in the BM while the lowest in the WNZ on root surface. The corrosion resistance of WNZ is much superior than that of BM, and WNZ on top surface is slightly superior than that on root surface. The maximum corrosion depth in BM is 145.9 μm while the maximum corrosion depths in WNZ on top surface and root surface are 46.3 μm and 84.1μm respectively.