A trade-off between strength and corrosion resistance is usually found in Al alloys. In this work, we attempt to overcome the strength-corrosion trade-off in an Al-1wt%Mg binary alloy by a surface mechanical treatment. Microstructure and chemical composition of Al Mg alloy with and without treatment were investigated by using SEM, TEM, XRD, SIMS and XPS techniques. After treatment, ultrafine grains with an average size of 433 nm are presented in the topmost ~5 μm layer, showing a significant grain refinement. The results of SIMS and XPS indicate that the surface segregation of Mg is evident for the coarse-grained sample, while for the treated sample Mg is absent on the topmost 10 nm-thick surface layer. The hardness increased by ~200 % and the corrosion rate decreased by ~60 %. Deformation-induced grain refinement, low-angle grain boundaries, strain strengthening effects and the redistribution of Mg element in the surface layer contribute to the simultaneous improvement of strength and corrosion resistance. Such plastic deformation treatment provides a novel strategy for effectively improving the strength and corrosion resistance of Al Mg alloys. Gradient structure fabricated by surface mechanical treatment overcomes the trade-off between strength and corrosion resistance in Al-1wt%Mg alloy. Deformation-induced grain refinement and depletion of Mg in the surface layer contribute to the simultaneous improvement of strength and corrosion resistance. [Display omitted] • Ultrafine grains averaging 433 nm at the topmost surface fabricated in Al-1wt%Mg • Hardness increases by ~200 %, corrosion rate decreases by ~60 %. • Overcoming the strength-corrosion trade-off in Al-1wt%Mg alloy. [ABSTRACT FROM AUTHOR]