Electrodeposition of alloys and compounds from high-temperature molten salts

This paper reviews the development of the electrodeposition of a variety of types of alloys and compounds from high-temperature molten salts. The electrodeposition from high-temperature molten salts has several distinct potential advantages. Firstly, molten salts can offer a much larger operative temperature range than other electrolytes such as aqueous electrolytes, which greatly expands the material systems that can be prepared by this method. Molten-salt electrodeposition is also able to obtain reactive metals (e.g., Al and Mg) and refractory alloys and compounds that are difficult or unable to be electrodeposited from aqueous solutions. Additionally, the electrodeposition from high-temperature molten salts contributes to the formation of strongly adherent coatings because the diffusion process enables the metallurgical bonding between the coating and the substrate. Therefore, a wide variety of alloys and compounds have been prepared by the molten-salt electrodeposition. The reviewed materials in this work are categorized into light metal alloys, transition metal alloys, rare-earth containing alloys and metal-containing compounds and special attention is paid to the reactive metals and refractory alloys and compounds. The electrochemical processes and growth mechanisms of the coatings formed in molten salts are described. The relationship among the preparation parameters, structures and properties is discussed. Finally, the development trend of the molten-salt electrodeposition is summarized and future work that should be carried out is proposed.