Electrodeposition of nanocrystalline nickel and cobalt coatings

Abstract

The importance of nanostructured deposits and methods for achieving them are considered. The scope for nickel and cobalt nanocrystalline single metal deposits is summarised and developments in the last decade are highlighted. In each case, chemical composition, phase composition and crystal structure are included. Nanostructure, physical and mechanical properties (including corrosion resistance) v. bath type and composition (including pH and electrolyte additives) together with plating conditions, including current density, temperature and agitation are summarised. While the majority of published studies have featured nickel, the more expensive cobalt has also been considered due to its better corrosion and high temperature oxidation resistance in some environments. An overall comparison between the two metals is made. The major applications of nanocrystalline nickel have been in wear and corrosion resistant coatings, particularly as a hard chromium replacement, but speciality emerging uses include catalytic electrode surfaces in water electrolysis. Future research needs are briefly listed.