Abstract A dense nanocrystalline Ni coating was successfully electrodeposited on Mg–3.0Nd–0.2Zn–0.4Zr (wt.%, NZ30K) alloy from a choline chloride–urea (1:2 molar ratio) eutectic-based ionic liquid (1:2 ChCl–urea IL) on the basis of an appropriate pretreatment. A Cu underlayer was pre-plated from a pyrophosphate based solution to avoid the severe corrosion and replacement reaction of NZ30K alloy in the IL electrolyte. The evolution of surface morphologies, compositions and phase structures of the pretreatment films and Ni coating were studied in detail. The uniform, smooth and dense nanocrystalline Ni coating possessing good adhesion to substrate has been proved by thermal shock test. Potentiodynamic polarization test in 3.5 wt.% NaCl solution showed that the Ni coating significantly improved the corrosion resistance of NZ30K alloy by nearly two orders of magnitude. Open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) during long-term immersion test further demonstrated that the Cu/Ni coating could provide an effective protection for NZ30K alloy from corrosion up to ∼336 h. The high corrosion resistance of the coating can be attributed to the dense nanocrystalline Ni structure and the synergistic effect of electrochemical protection between Ni coating and Cu underlayer.

中文翻译：

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共晶基离子液体电沉积在 Mg-Nd-Zn-Zr 合金上的高耐腐蚀纳米晶 Ni 涂层的表征

摘要 在 Mg-3.0Nd-0.2Zn-0.4Zr (wt.%, NZ30K) 合金上以氯化胆碱-尿素（1:2 摩尔比）共晶离子液体（1:2 ChCl–尿素 IL）基于适当的预处理。Cu 底层由基于焦磷酸盐的溶液预镀，以避免 NZ30K 合金在 IL 电解质中的严重腐蚀和置换反应。详细研究了预处理膜和镍涂层的表面形貌、成分和相结构的演变。热冲击试验证明了均匀、光滑、致密的纳米晶镍镀层对基体具有良好的附着力。3.5 wt. 动电位极化测试 % NaCl 溶液表明，Ni 涂层使 NZ30K 合金的耐腐蚀性能显着提高了近两个数量级。长期浸泡试验中的开路电位 (OCP) 和电化学阻抗谱 (EIS) 进一步证明，Cu/Ni 涂层可以为 NZ30K 合金提供有效的保护，使其免受长达 336 小时的腐蚀。涂层的高耐腐蚀性可归因于致密的纳米晶 Ni 结构以及 Ni 涂层和 Cu 底层之间电化学保护的协同作用。