Abstract:Nanocrystalline cobalt coatings were produced from cobalt sulfate based electrolytes by using pulse current electrodeposition technique. The effects of bath composition and electrodeposition condition on current efficiency, morphology, structure and hardness of the coatings were investigated and the optimum deposition condition was determined. It was found that increment of cobalt sulfate concentration and sodium dodecyl sulfate (SDS) concentration in the bath had a negligible effect on microhardness of the coatings, while they were effective on electrodeposition current efficiency. Adding saccharin to electrodeposition bath decreased crystallite size of hexagonal close-packed (hcp) cobalt films and increased their microhardness without significant effect on current efficiency. Smoother and less defective coatings were also obtained from baths containing SDS and saccharin. The results revealed that both the current efficiency and microhardness were changed by variation of peak current density and duty cycle. Besides change of smooth morphology of the coatings to needle-shaped one, crystallite sizes and preferred orientation also varied with increasing the current density and duty cycle.

Key words: cobalt coating; pulse electrodeposition; saccharin; sodium dodecyl sulfate; characterization; current efficiency; microhardness