The welding apparatus and associated method are provided. The welding apparatus includes a welding tool for forming a weld joint along the surface of at least one workpiece. The welding apparatus also includes a compression tool for selectively inducing a layer of residual compressive stress in at least a portion of the surface of the weld joint and the surface of the at least one workpiece to thereby improve the material properties of the workpiece, including corrosion resistance and fatigue strength.