Abstract: Ni60/WC/Cu directionally structured composite coatings were prepared using a combined process of flame spraying, induction remelting, and directional cooling. The electrochemical corrosion characteristics and immersion corrosion performance of the coatings was evaluated in a 3.5 wt.% NaCl solution, and the corrosion behavior of the coatings was discussed.The results indicated that all coatings exhibit typical activation-passivation-transpassivation corrosion characteristics in the 3.5 wt.% NaCl solution, with their electrochemical impedance spectra showing distinct capacitive behavior. The polarization resistance (R_p) and charge transfer resistance (R_ct) of the coatings initially increase and then decrease with increasing Cu content (1 wt.%~5 wt.%), and the corrosion resistance of the coatings showed a trend of first increasing and then decreasing. The 3 wt.%Cu/10 wt.%WC coating demonstrate the most positive corrosion potential (E_corr), the lowest corrosion current density (I_corr), and the highest R_ct. The dense and uniform composite oxide passive film is formed on the coating surface composed of NiO, Cr₂O₃, Cu₂O, and WO₃, which effectively prevent further penetration and corrosion by Cl^－, enabling the coatings to exhibit excellent corrosion resistance in the 3.5 wt.% NaCl solution.

Key words: Ni60/WC/Cu directionally structure composite coating, electrochemical corrosion, immersion corrosion, 3.5 wt.% NaCl solution