目的 通过电沉积方法在镁锂合金表面制备具有高红外发射率以及高导电率的镀层,满足其在太空中散热以及电磁屏蔽的需要.方法 通过前处理工艺(碱洗→酸洗→预钝化→化学镀镍磷→电镀铜)提高镁锂合金基体的耐蚀性能以及与后续镀层的结合力,并在此镁锂合金前处理工艺的条件下,电沉积多孔Zn-Ni合金镀层.通过热循环测试和电化学方法评价各镀层的电化学腐蚀行为和各镀层之间的结合力.结果 各镀层之间的结合力良好,化学镀Ni-P层、电镀Cu层和多孔Zn-Ni层的耐蚀性能均优于镁锂合金基体,该组合镀层的协同作用可以有效地保护镁锂合金基体,提高其耐蚀性.结论 最外层多孔Zn-Ni合金镀层主要由Ni2Zn11、NiO、NiS组成,其红外发射率为0.90,电阻率小于0.01 mΩ/cm.这表明多孔结构可以有效提高金属合金镀层的红外发射率,并保持合金镀层的高导电性.
The work aims to prepare a coating of both high electrical conductivity and infrared emissivity on Mg-Li magnesium alloy by hydrogen evolution method in order to meet the needs of thermal control and electromagnetic shielding in space.Corrosion resistance of the substrate was improved by a series of pretreatment processes (alkali cleaning→acid pickling→pre-passivation→electroless plating Ni-P →plating Cu),and adhesion to the following coatings was improved by plating the Cu interlayer.Porous Zn-Ni alloy coating was electrodeposited based on this pretreatment process of Mg-Li alloy.The corrosion behavior of all coatings and adhesion among them were evaluated by virtue of thermal cycle test and electrochemical method.As a result,adhesion of all the coatings completely met the technical standard applicable to satellites in space.The corrosion resistance of Ni-P coating,Cu coating and porous Zn-Ni coating was superior to that of Mg-Li alloy.The synergistic effect of these multi-layer coatings could protect the Mg-Li substrate and increase its corrosion resistance significantly.The outmost layer of porous Zn-Ni coating was composed of Ni2Zn11,NiO and NiS which shows high infrared emissivity of 0.90 and electrical resistance of ＜0.01 mΩ,/cm.It can be found that the porous structure can considerably increase the infrared emissivity while maintaining high electrical conductivity of metal alloy coatings.
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