Despite the extensive use of 7xxx aluminum alloys in aerospace, intergranular corrosion is yet to be appropriately addressed. In this work, in situ rolling friction stir welding (IRFSW) was proposed to improve the corrosion resistance of joints via microstructural design. A gradient-structured layer was successfully constructed on the surface of the joint, and the corrosion resistance was improved by in situ rolling. The intergranular corrosion depth of the IRFSW joint was reduced by 59.8% compared with conventional joints. The improved corrosion resistance was attributed to the redissolved precipitates, the disappearance of precipitate-free zones, and the discontinuous distribution of grain boundary precipitates. This study offers new insights for enhancing the corrosion resistance of aluminum alloy FSW joints.