Hardening precipitation in an intergranular-corrosion desensitized alloy, AA6056-T78, is characterized in comparison with that in AA6013 and AA6082 alloys. To extract quantitative information, image-analysis is applied to dark-field images and selected-area diffraction patterns, along with standardless EDX spectroscopy. The central result is that both needle-shaped and lath-shaped precipitates have a similar chemical composition (except for Al content remaining undetermined in this study) to each other and, furthermore, to that of most of the grain boundary precipitates, normally in a more advanced state of precipitation kinetics than those in the grains.