The effects of the surface ultrasonic impact treatment on the microstructure and corrosion resistance of the wrought low-alloyed, low-cost Al–Mg–Si alloy of 6060 type were investigated. The alloy has high plasticity, the ability for hot extrusion, and high corrosion resistance, which are excellent characteristics for various applications. The low strength of the alloy, however, is its main disadvantage. Of great interest is the search for additional methods of hardening the alloy. The primary task of this research investigation has been to study the possibility of improving the mechanical properties of the alloy using surface severe plastic deformation in combination with different types of thermal treatments. One of the methods of surface plastic deformation is ultrasonic impact treatment (UIT). The use of high-power ultrasonic energy in the surface treatment of materials leads to fundamental changes in the structure of the surface and subsurface layers. The study of the effect of ultrasonic impact treatment on the structure of the Al–Mg–Si alloy surface showed that the initial structural state of the alloy significantly affected the mechanism of relaxation of internal stresses generated by impact-cyclic loading. Strengthening was caused by internal stresses in the matrix. The UIT-induced increase in the alloy microhardness was 24%. As a result, the Al–Mg–Si alloy specimens processed by surface ultrasonic impact treatment exhibit improved corrosion resistance compared with their original state.