Study On The Technology Of Zinc And Aluminum Electroplating In Ionic Liquid

NdFeB magnets which as high-tech materials in National863Plan of China are widely used in the fields of communication, computers, military and medical treatment. In our country, zinc plating, nickel plating, and chemical nickel-plating are used in the technology of NdFeB surface protection mainly. Traditional electroplating technology often proceed in water solution, which often leads to hydrogen evolution reaction, such as hydrogen embrittlement, low current efficiency and environmental pollution. Hence, how to obtain high quality coating and reduce environmental pollution is a top priority in green chemistry now. Electroplating in ionic liquid often takes place in anhydrous circumstance and room temperature, which could prevent the hydrogen embrittlement and improve the quality of coating by adding organic additives. As a result, it is a promising surface protection technology.Aluminum has the properties of excellent gloss, outstanding malleability, high conductivity and thermal conductivity, and high corrosion resistance. Aluminum is active metal, possessing a standard electrode potential of-1.676V, The founding of ionic liquid provides excellent medium for electroplating Al.In this paper we have prepared different types of ionic liquids, and selected the optimal plating system, applying in the technologies of electroplating Zn on NdFeB magnet and electroplating A1on copper-based system. The main contents are shown below:①Determining the relation between the ionic liquid and the temperature difference by conductivity meter;②Measuring cyclic voltammetry curves in ionic liquid electrodeposition;③Discussing the influence of various factors on plating effect;④Morphology, purity, physical property and decay resistance of coating are determined by SEM, XRD, thickness test, adhesive force test, and neutral salt spray test. Results show that:In the experiment of electroplating Zn on NdFeB magnet, the result got from the urea-KBr-NaBr-formamide-ZnCl2ionic liquid system is the best. Further result suggests that the conductivity of ionic liquid increases with the increase of temperature. The coating with compact and uniform microstructure (determined by SEM) is prepared by the conditions that addictive is10mL·L-1, electric current density is1A/dm2, temperature is30℃, and electroplating maintain for20min under pulse plating power with magnetic stirring. XRD results show that the electrical crystallization product grows along the (101) crystal face first, and electrocrystallinity is very high. The average thickness of passivating coating is23.19μm, whose binding force achieves the first grade standards. And there is no rust spot after48h in neutral salt spray test.In experiment of electroplating Al on copper-based system, the result got from the urea-KBr-NaBr-formamide-AlCl3and [Bmim]Cl-AlCl3ionic liquid system is the best. Since imidazole system has been widely investigated, urea-KBr-NaBr-formamide-AlCl3system is studied in present work. Further results reveal that:the conductivity of ionic liquid increases with the increase of temperature. The coating with compact and uniform microstructure is prepared by the conditions that electric current density is50mA/dm, temperature is70℃, and electroplating maintain for45min under pulse plating power. XRD results show that the electrical crystallization product grows along the (200) crystal face first, and electrocrystallinity is very high. The average thickness of passivating coating is14.76μm, whose binding force achieves the first grade standards. And there is no rust spot after96h in neutral salt spray test.In a word, Zn coating is prepared on NdFeB magnet in ionic liquid, Al coating is prepared on copper-based system, and the optimal plating conditions is summarized. The study presents a new method for low temperature, low energy consumption and green plating conditions.