Electrodeposition And Properties Of Zn-Ni Alloys In Low Eutectic Ionic Liquids

Deep eutectic liquid was prepared with choline chloride（ChCl）and urea（Urea）for electrodeposition of Zn-Ni alloy.Infrared spectrum analysis（IR）was used to study the functional groups of synthetic raw materials（ChCl and Urea）and synthetic ionic liquids.The electrical conductivity of ionic liquid was measured and studied with conductivity meter.Cyclic voltammetry（CV）was used to systematically study the electrochemical window of ionic liquid,the electrochemical behavior of Zn²⁺and Ni²⁺,the reversibility of the redox reactions of Zn²⁺and Ni²⁺,the reaction control mode and the related kinetic parameters.The mechanism of electrocrystallization of Zn²⁺and Ni²⁺electrodeposition was studied by using timing amperometric curve（CA）.Scanning electron microscopy（SEM）and energy dispersive spectroscopy（EDS）were used to study the electrodeposition process of Zn²⁺and Ni²⁺,the microstructure and elemental composition of the coatings.The phase composition of the metal coating was analyzed by X-ray diffractometer（XRD）.The mechanism of ChCl-Urea system was analyzed by UV-Vis.The corrosion resistance was analyzed by potentiodynamic polarization curve（Tafel）and impedance frequency scan（EIS）.The physicochemical properties of ionic liquids and electrodeposition of metals were studied and analyzed by the above test and characterization methods,and the following conclusions were drawn according to the research results:（1）Through conductivity meter,cyclic voltammetry test,infrared spectrum analysis（IR）and UV-VIS spectroscopy to determine the electrochemical window of ChCl-Urea ionic liquid,determine the interaction of nickel ion and choline chloride Urea to produce complex[NiCl3]^-,It is confirmed that the addition of salt of metal will simply produce physical mixing with the system without changing the characteristics of ionic liquid.（2）In ChCl-Urea-ZnCl₂-NiCl₂·6H₂O,metal Ni was preferentially deposited in Zn during the co-deposition of Zn-Ni alloy,and the nucleation mechanism was three-dimensional instantaneous nucleation controlled by diffusion.Temperature and potential have obvious influence on the three nucleation processes of Zn-Ni alloy（three-dimensional nucleation/growth process controlled by diffusion,adsorption process and water reduction process）.The contribution rate of nucleation in each process was calculated.The complicity can control the contribution rate of nucleation through the change of temperature and applied potential,so as to obtain good quality coatings.（3）The additive H₃BO₃（BA）can improve the nucleation rate,reduce the crack of Zn-Ni coating,refine the grain,and make the coating smooth and compact.The additive Na Br can promote the deposition of Zn-Ni alloy,which can increase the deposition rate and nucleation rate,so that there are many particles of different sizes on the surface of Zn-Ni alloy.The additive BA+Na Br is different from the additive BA and Na Br separately.The deposition rate and nucleation rate of Zn-Ni alloy are between the two,and the coating is smooth and the grain size is small.The addition of additive can greatly improve the morphology of the coating.（4）The presence of appropriate water had a certain influence on the electrochemical window of ChCl-Urea system and the margin of group vibration frequency.The presence of adequate water（0-5 wt%）promoted the deposition of Zn²⁺and Ni²⁺.Moreover,the addition of water has no obvious effect on the nucleation mechanism of Zn-Ni alloy.The coating quality was significantly improved with the increase of water content（0-5 wt%）,and the presence of water could indeed affect the composition of the coating.This provides an important reference for the controllable preparation of Zn-Ni alloy coatings.