Electro-deposition of nickel, on reactor seal discs

The effect of plating variables, acidity, current density and temperature on hardness of nickel deposited from purified nickel sulfamate bath has been investigated and optimum conditions for electrodeposition of nickel plating of hardness 160-170 VHN on reactor seal discs are established. Sodium lauryl sulfate was added as a wetting agent to the bath to overcome pitting tendency of the deposit. Factors affecting hydrogen absorption by electrodeposited nickel are also discussed. It is observed that : (1) at a pH 3.5 - 4.0 the decomposition rate of sulfamate salt is almost negligible and is the best value for bath operation, (2) at 15 A/dm2 the hardness value is consistently around 160-170 VHN, (3) the temperatures less than 500C give harder deposits and the bath is best operated at temperature 50-600 C and (4) annealing of the plated discs substantially reduces the hardness. (M.G.B.)