Elelctrodeposition And Properties Of Metal Coatings From Deep Eutectic Solvents

Metal matrix coatings are prepared by codepositing metal or non-metal particels into an electrodeposited metal matrix. The incorporation of particulate material into metal coatings allows alloys or metal composites to be produced with improved hardness, toughness, wear resistance and self-lubricating due to the reinforcement of the second phase particles. Compared with laser surface technology and thermal spraying technology, electrodeposition is proved to be a simple and economic method to produce dense metal, alloy and metal composite. However, the usual procedure of metal electrodeposition is mostly based on aqueous solutions of which there are limitations including the poisonous plating baths, the necessity for complexing agents and grain-refinement additives, and the difficult handling of hydrogen evolution processes which leads to hydrogen embrittlement. In this work, the ChCl-EG deep eutectic solvent is used to produce Ni-Co, Ni-P, Ni-PTFE and Cu coatings and the microstrutures and properies of these coatings are investigated from viewpoint of material science.Ni-Co alloys are electrodeposied from a ChCl-EG based DES containing NiCl2·6H2O and CoCl2·6H2O at room temperature. Comparative studies on deposition mechanism, micro-structure, and electrochemical properties between Ni and Ni-Co alloys films were investigated. Surface morphology and chemical composition of these films are significantly dependent on the Ni2+and Co2+concentrations in the electrolytes. The electrodeposition of Ni-Co in the DES-based electrolytes does not follow the anomalous codeposition process, which is frequently observed in the aqueous electrolytes. The as-deposited Ni-Co alloys possess face-centered cubic structures and refined grains. The anti-corrosion of Ni-Co alloys gets worse as the more Co content the Ni-Co films have. It is due to the much thinner Ni-Co alloy films with embedded Cl.Ni-P alloy coatings are firstly electrodeposited from the non-aqueous ChCl-EG based electrolytes. The nucleation and growth of Ni and Ni-P alloy coatings onto a Pt electrode from the ChCl-EG based electrolytes belong to instantaneous nucleation and a three-dimensional growth under diffusion control. The deposition potential and time have a remarkable effect on the surface morphology of deposits. The structure of Ni-P deposits converts from crystalline to amorphous structure as the phosphorus content in the coating increases and corrosion resistance is enhanced due to the amorphous structure.Electrodeposition process of Ni-polytetrafluoroethylene (PTFE) composite coatings is limited to use aqueous plating bath where nonionic/cationic wetting agents usually are necessary to prohibit the hydrophobic PTFE particles being coagulated. This study proposes a novel electrolyte for the depositing Ni-PTFE composite coatings which is formed in a deep eutectic solvent (DES). The DES with a non-aqueous nature allows the PTFE particles well be dispersed in the electrolyte without the additive of any wetting agents. The Ni-PTFE composite coatings are successfully electrodeposited from the proposed DES-based plating bath which is confirmed by the scanning electron microscope and X-ray energy dispersive spectroscope. Deposition mechanism, microstructure, and properties of the composite coatings are investigated. The Ni-3.1wt.%PTFE composite coating shows a hydrophobic behavior with a contact angle of about121±1°and an enhanced wear resistance than the pure Ni coating due to the incorporation of PTFE.In the work of Cu electrodeposition, a comparative study on the deposition mechanism, microstructure, and electrochemical property of Cu electrodeposits from the base plating bath of CuCl2·2H2O in ChCl-EG based eutectic solvent with the absence and presence of the additive of EDA. The base electrolyte was unstable for a long period of Cu electrodeposition process and the as-deposited Cu film consisted of typically columnar grains with a strongly (111) preferred texture. Upon the introduction of EDA to the base electrolyte, the nucleation and growth of Cu deposits were strongly inhibited, thus producing a much smooth and compact surface with finer grains. All electrodeposited Cu films from the ChC1-EG based electrolytes were pure Cu and had an fcc crystal structure revealed by EDS and XRD analyses, respectively. The addition of EDA to the base electrolyte had a positive effect on enhancing the corrosion resistance of Cu deposits.