Cu–Ni–Fe alloy coating was prepared on low-carbon steel by surface alloying. The surface heat treatment of coated low-carbon steel was performed at 700°C, 800°C, 900°C and 1000°C for 3h under hydrogen atmosphere. The structure and microstructure of coatings were separately analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). A series of electrochemical analysis was carried out to examine the corrosion resistance of Cu–Ni–Fe alloy coatings in borate buffer solution. Results indicated that a uniform and homogeneity Cu–Ni–Fe alloy coating constituted of γ-phases was prepared on the surface of low-carbon steel at 1000°C, which promoted the formation of compact passive film. The passive film significantly improved the substrate's corrosion resistance in alkaline solution. ► Cu–Ni–Fe alloy coating was prepared on low-carbon steel. ► A compact and uniform Cu–Ni–Fe alloy coating constituted of homogeneous γ-phases was prepared at 1000°C ► The Cu–Ni–Fe alloy coating is passive and provides corrosion protection in alkaline solution.