室温离子液体中电沉积高耐蚀性Ni-Mn薄膜

目的提高AZ91D镁合金的耐腐蚀性能。方法通过电沉积方法在氯化胆碱-尿素离子液体中于镁合金表面电沉积Ni-Mn合金膜层。经过均一化前处理,在镁合金表面电沉积铜层,以提高后续Ni-Mn合金膜层与基体的结合力。利用扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)研究了Mn元素对膜层微观形貌、成分和相结构的影响,并通过电化学方法评价了镀层的电化学腐蚀行为。结果引入Mn元素后,膜层表面微观形貌从锥状演变为肿瘤状,且Ni-Mn合金膜层的Mn含量取决于电流密度,其含量随着电流密度的增加而增加。与纯Ni膜相比,引入少量Mn元素可以提高其耐腐蚀性能,然而引入过多的Mn元素,膜层的耐腐蚀性能将弱于纯Ni膜。结论当电沉积Ni-Mn膜层含有3.078%(原子数分数)Mn时,具有最佳的耐腐蚀性能,其自腐蚀电流密度Jcorr=0.301μA/cm2,自腐蚀电位Ecorr=-0.157 V(vs.SCE)。

Electrodeposition of Ni-Mn Films of High Corrosion Resistance at Room Temperature in Ionic Liquids

The work aims to improve corrosion resistance of AZ91D magnesium alloy.Ni-Mn alloy film was electrodeposited on the surface of magnesium alloy in the choline chloride-urea ionic liquid by electrodeposition method.After homogenization pretreatment,the copper layer was electrodeposited on the surface of magnesium alloy to improve the adhesion between subsequent Ni-Mn alloy film and the substrate.The effects of Mn element on the surface morphology,chemical composition and phase structure of the film were studied by using scanning electronic microscopy (SEM),energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction spectroscopy (XRD).Once Mn was incorporated into the film,the surface morphology transformed from pyramid-like to tumor-like clusters.Moreover,Mn content of Ni-Mn alloy film rest on current density and increased as the current density increased.Corrosion resistance of the coating could be improved by introducing a little Mn compared with pure Ni film.However,the corrosion resistance of the film was weaker than that of the pure Ni film when too much Mn was introduced.The Ni-Mn alloy film,when comaining 3.078at.％ Mn,shows the best corrosion resistance with self-corrosion current Jcorr of 0.301 μA/cm2 and corrosion potential Ecorr of-0.157 V (vs.SCE).