A method for constructing a welded construction, including the steps of: (a) providing separate component parts of the construction and (b) welding the separate parts together with an Al--Mg--Mn weld filler alloy having a good corrosion resistance and improved strength levels. The separate component parts having the following composition (in weight percent): Mg 4.9 to 6.0; Mn 0.6 to 1.2; Zn 0.25 to 1.5; Zr 0.05 to 0.25; Cr 0.3 max.; Ti 0.2 max.; Fe 0.5 max.; Si 0.5 max.; Cu 0.25 max.; Sc 0.3 max., balance inevitable impurities and aluminium. The Al--Mg--Mn weld filler alloy having the following composition (in weight percent): Mg 7.0-9.5; Mn 0.9-2.0; Zn 0.2-0.9 Zr.ltoreq.0.3; Cr.ltoreq.0.5; Sc.ltoreq.2.8; Cu.ltoreq.0.5; Fe.ltoreq.0.5; Si.ltoreq.0.5; Ti.ltoreq.0.3, the balance aluminium and incidental elements and impurities.