Leave the sprayed area alone for 10 to 15 minutes, enabling WD-40 to penetrate deep into the concrete's pores as well as the rust layers to break up rust deposits effectively.
Use a stiff brush like a wire bristle or an old toothbrush to rub in circular movements against rust stains loosened with WD-40. This helps lift away any pieces dislodged by WD-40.
Rinse the area with cold water and mild dish soap to eliminate residue build-up. If the rust doesn't come off after one scrub, repeat the steps until all traces of rust are gone.