电刷镀Ag-Bi合金镀层的结构与耐蚀性能研究  

Investigation on Structure and Corrosion Resistance of Ag-Bi Alloy Coating Fabricated by Brush Plating

作　　者：杜宝帅 闫芝成 张忠文 张都清 索帅 李新梅 DU Baoshuai;YAN Zhicheng;ZHANG Zhongwen;ZHANG Duqing;SUO Shuai;LI Xinmei(State Grid Shandong Electric Power Research Institute,Jinan 250002,China)

机构地区：[1]国网山东省电力公司电力科学研究院,济南250002

出　　处：《表面技术》2024年第4期110-116,183,共8页Surface Technology

基　　金：国网山东省电力公司科技项目(520626210020)。

摘　　要：目的采用电刷镀技术制备Ag-Bi合金镀层,揭示镀层的微观结构特征与耐腐蚀性能。方法基于酸性硫代硫酸钠无氰镀液体系,利用电刷镀技术在铜基体上制备了纯银以及Ag-Bi合金镀层。利用XRD和SEM分析了镀层的物相组成和微观形貌,采用显微硬度计测试了镀层的硬度,通过极化曲线和电化学阻抗谱对镀层的耐腐蚀能力进行了表征。结果电刷镀制备的合金镀层均由面心立方结构Ag(Bi)过饱和固溶体组成,在Ag-15.64Bi合金镀层中还形成了六方结构α-Bi相。所制备的镀层具有纳米级晶粒尺寸,范围为13.5~21nm。与纯Ag镀层相比,电刷镀Ag-Bi合金镀层的致密性和平整度明显提高。合金镀层的硬度随着Bi含量的增加而增加,最高为220.7HV。镀层的自腐蚀电位和电荷转移电阻随着Bi含量的增加先增加后减小,腐蚀电流密度呈现相反趋势,Ag-4.52Bi镀层具有最佳的耐腐蚀能力,其自腐蚀电位为-0.189 V,腐蚀电流密度为1.76×10^(-2) mA·cm^(-2),电荷转移电阻为1635Ω·cm^(2)。结论通过在酸性硫代硫酸钠镀液中加入硝酸铋,可以电刷镀制备Ag-Bi合金镀层。Bi元素含量对镀层的显微硬度和耐腐蚀能力均具有显著影响。随着镀层中Bi元素的增加,固溶强化、细晶强化效应使镀层的硬度明显增加。合金镀层中孔隙和缝隙等结构缺陷的减少阻碍了腐蚀介质的渗入,Bi元素对镀层钝化膜的形成具有促进作用,最终使镀层的耐腐蚀性能得到提升。Silver coating has been used extensively in the field of power electronics and aerospace industry.However,due to its inherent FCC crystal structure and sensitivity to corrosive factors such as Cl-and SiO2,it suffers from low wear and corrosion resistance.Non-cyanide silver alloy plating shows promise in improving the comprehensive properties of silver coating.The work aims to fabricate Ag-Bi alloy coating by brush plating technology and reveal its characteristic microstructure and corrosion resistance property.Based on acidic non-cyanide sodium thiosulfate plating bath,pure Ag and Ag-Bi alloy coatings were synthesized on copper by brush plating.Bi(NO)3 was used as the source of Bi element in the coating and varied in the plating bath to control the content of Bi in the alloy coating. T2 copper was used as the substrate, and it was ground with sand paper and subject to electro-cleaning and activation before the brush plating process. XRD and SEM were used to analyze the phase constituent and micro-morphology. Microhardness tester was employed to measure the hardness of the coatings. Corrosion resistance of the coatings was characterized by polarization curve and electrochemical impedance spectroscopy. Results showed that FCC supersaturated Ag(Bi) phase was presented for all the coatings, and hexagonal α-Bi phase was found in the Ag-15.64Bi alloy coating, which indicated the phase separation for this coating. The phenomenon of Ag(Bi) diffraction peak shifting to the left was found due to the solid solution effect of Bi element. The brush plated coatings possessed nano-sized grain structure which was in the range of 13.5-21 nm. Surface of the pure Ag coating showed the cauliflower-like morphology, while Ag-Bi coatings presented much refined granular structure. Compared with the pure Ag coating, brush plated Ag-Bi alloy coatings showed improved compactness and surface roughness. With the increase of Bi content in the alloy coating, the microhardness increased accordingly, reaching a maximum value of 220.7HV for the

关 键 词：电刷镀 Ag-Bi镀层 耐蚀性 显微硬度 

分 类 号：TG174.44[金属学及工艺—金属表面处理]