Abstract: Here were studied the mechanical properties, corrosion resistance, and the ferrite-austenite (α-γ) dual-phase structure of the overlay of duplex stainless steel coated on the low-carbon steel by CO₂ flux-cored arc welding (FCAW) and cooled in water and air. The results showed that the methods of water or air cooling had no significant effect on the mechanical properties of the surfacing layer; that the ferrite content of the surfacing layer cooled in water could reach 45.17%, which was more closed to equilibrium than in air cooling, and that the surfacing layer was mainly composed of block ferrite and acicular austenite distributed along the ferrite crystal or sub-crystal boundaries; that the surfacing layer cooled in water had superior corrosion resistance and the average corrosion rate was 0.488 mm/a.