Electrodeposition of Ni-P composite coatings: A review

Ni-P coatings produced by electrodeposition have important mechanical, tribological and electrochemical properties. They can also exhibit catalytic activity and beneficial magnetic behaviour. With subsequent thermal treatment, the hardness of such Ni-P coatings can approach or exceed that of hard Cr coatings. Electrochemical codeposition of homogeneously dispersed second phase particles within the Ni-P matrix can enhance deposit properties and meet the challenging demands on modern engineering coatings. A general overview of research work on the electrodeposition of Ni-P composite coatings containing included ceramic or solid lubricant particles is provided. Advances in research into Ni-P composite layers reinforced by SiC, B4C, WC, Al2O3, SiO2, TiO2, CeO2, MWCNT, MoS2, WS2, TiN, hexagonal BN, PTFE and their combinations are considered. Major models proposed for the codeposition of particles, the influence of bath hydrodynamics and control of operational parameters are illustrated by examples. Important trends are highlighted and opportunities for future R & D are summarised.