The current research has assessed the correlation between welding parameters and corrosion behaviour for friction stir welded 6056 aluminium alloy. Different thermal treatments and welding parameters were considered. For the welding parameters studied in this project, the data strongly indicate that sensitivity to corrosion is linked to the welding parameters employed. Substantial differences were found for the higher and lower speed welding parameters, with the lower speed parameters appearantly resulting in less corrosion resistance. The most widespread form of corrosion observed was pitting; however, intergranular corrosion (IGC) was also seen. While the T78 thermal treatment appears to decrease the corrosion resistance of the parent alloy, the weld region tends to improve, with the nugget being cathodic.