Effect of Organic Additives on the Hardness of Ni Electrodeposited from Sulfamate and Watt’s Solutions

Abstract

Ni electrodeposition was galvanostatically conducted over a current density range 1–5000 A/m² from unagitated sulfamate (323 K) and Watt’s solutions (313 K) containing polyethylene glycol (PEG) or saccharin to examine the effect of the C and S contents in the deposit and the texture on the hardness of the deposited Ni. The C content in Ni deposited from Watt’s solutions containing PEG was significantly higher than that from the sulfamate solution. The S content in deposits from sulfamate and Watt’s solutions containing saccharin differed slightly, except at 2000 A/m². The hardness of the deposited Ni increased with increasing C and S contents, and the rate of increase in hardness decreased at S content above 0.02 mass%. The texture of the deposited Ni changed from a field-oriented texture to an unoriented dispersed type when C and S were co-deposited with Ni by the addition of PEG and saccharin. The hardness of the unoriented dispersed type of Ni deposit was greater than that of the field-oriented type of Ni deposit.