采用火焰喷涂-感应重熔-定向冷却协同工艺制备Ni60/WC/Cu定向结构复合涂层.评估涂层在3.5 wt.% NaCl 溶液中的电化学腐蚀特性和浸泡腐蚀性能,探讨涂层在3.5 wt.% NaCl溶液中的腐蚀行为.结果表明:涂层在3.5 wt.% NaCl溶液中均呈现典型的活化-钝化-过钝化腐蚀特征,其电化学阻抗谱表现出明显的容抗特性.随着Cu(1 wt.%~5 wt.%)含量的增加,涂层极化电阻RP和电荷转移电阻Rct先增大后减小,涂层的耐腐蚀性呈现先升高后降低的趋势.3 wt.%Cu/10 wt.%WC涂层的腐蚀电位Ecor移至最正,腐蚀电流密度Icorr减至最小,同时具有最高的Rct.涂层表面形成了致密均匀的由NiO、Cr2O3、Cu2O和WO3组成的复合氧化物钝化膜,有效阻止了Cl－的进一步渗透侵蚀,使得涂层在3.5 wt.% NaCl中表现出良好的耐蚀性能.
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 (Rp) and charge transfer resistance (Rct) 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 (Ecorr), the lowest corrosion current density (Icorr), and the highest Rct. 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.
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