Study On Electrodeposition Of Ni-Fe And Ni-Ti Alloy By Ionic Liquid

Nickel alloy as protective and decorative coating has been widely used in steel and other materials to improve their corrosion resistance. The electrodeposition of nickel alloy in inorganic salt aqueous solution is the traditional method, but it exists problems such as complex process and high cost. As a new-style electrolyte, lots of metals and alloys have been electrodeposited, however, using ionic liquids instead of the conventional electrolyte is rarely reported at home and abroad. In this paper, the ChCl-urea-NiCl2-FeCl3 and [Bmim]Cl-EG-NiCl2-TiCl4 ionic liquids were used as the electrolytes for the electrodeposition of Ni-Fe and Ni-Ti alloy. The mechanism of electrodeposition of Ni-Fe and Ni-Ti alloy, composition, phase structure, morphology and corrosion resistance of the alloy coating have been been investigated systematically.Electrochemical analysis of ChCl-urea-NiCl2-FeCl3 ionic liquids shows that the metallic nickel deposited on the substrate induces the under potential deposition of metallic iron, resulting on the co-deposition of Ni-Fe alloys; When using glassy carbon electrode as working electrode, the deposition of Ni, Fe and Ni-Fe alloys follow the three-dimensional instantaneous nucleation/growth process which controlled by diffusion. Electrochemical analysis of [Bmim]Cl-EG-TiCl4 ionic liquids shows that Ti(â…£) can only be reduced to Ti(â…¡) and no metallic titanium deposited on the substrate, while in [Bmim]Cl-EG-NiCl2-TiCl4 ionic liquid, the metallic nickel deposited on the substrate induces the under potential deposition of metallic titanium, resulting on the co-deposition of Ni-Ti alloys.By studying the influence of current density, concentration of FeCl3, temperature on sediment composition, current efficiency and morphology,we can make a conclusion as follows:the Fe content increases in the alloy with the increase of current density and FeCl3 content, and decreases with the increase of temperature in ChCl-urea-NiCl2-FeCl3 ionic liquid; However, with the increase of current density, FeCl3 content and temperature, current efficient increases initially and decreases later; with the increase of current density, FeCl3 content and temperature, needle-like grain gradually grow in spherical particles, when the current density is 4 mA/cm2, the temperature is 348 K, NiCl2 content is 0.1 mol/L and FeCl3 content is 0.15 mol/L, the morphology of Ni-Fe alloy coating is the most compact; The coating is mainly composed of FeNi3 solid solution and Ni, besides, Fe0.64Ni0.36 phase is observed in alloy obtained.Electrodeposition of Ni-Ti alloy experiment shows that when the thickness of Ni-Ni alloy coating reaches a certain value, it would not increase and begin to strip, which leads a thinner coating with prolonging the electrodepostion time. The XPS analysis of Ni-Ti alloy coating shows that the surface of Ni-Fe alloy coating was completely oxidized to TiO2 and part of Ni2O3 because of the high chemical activity of Ti.Corrosion resistance experiments of Ni-Fe alloy show that the corrosion resistance of Ni-Fe alloy coating depends on the content of Fe, with the increase of Fe content, the corrosion resistance of the Ni-Fe alloy coating shows a trend of decrease at last after the increase initially. The corrosion resistance of Ni-Fe alloy exhibits best when the content of Fe is about 24.89 at%, in addition, the corrosion resistance of the alloy coating is superior to pure Ni.