Effect of current density and organic additives on the texture and hardness of Ni electrodeposited from sulfamate and Watt's solutions

Nickel electrodeposition was galvanostatically conducted over the current density range 500-2000 A/m2 in unagitated sulfamate and Watt's solutions at 323 and 313 K, respectively, to examine the effect of current density and organic additives on the texture, crystal orientation, and hardness of the deposited Ni. The overpotential for Ni deposition increased by the addition of polyethylene glycol (PEG) or saccharin in both sulfamate and Watt's solutions. The degree of increase in the overpotential in a PEG-containing solution was larger than that in a saccharin-containing solution. Nickel deposited from an additive-free solution showed a morphology of field oriented texture type with the preferred orientation of the {100} plane, while Ni obtained from a PEG- or saccharin-containing solution had the unoriented dispersed type without a preferred orientation in the region of some current densities. The region of the current density that resulted in the unoriented dispersed type in Watt's solution was larger than that in a sulfamate solution. The particle size of the deposited Ni decreased with the addition of PEG and saccharin. The hardness of the deposited Ni increased with PEG and saccharin, and was higher for the unoriented dispersed texture than for the field oriented texture. In additive-containing solutions, the hardness of Ni deposited from Watt's solution was higher than that from a sulfamate solution.