Abstract
The behavior of butynediol used as a brightner in nickel plating baths was studied measuring the concentration change of butynediol in the baths with plating time, and the carbon contents in nickel deposits. Butynediol was decomposed electrochemically to butanediol on the cathode surface at a definite rate controlled by diffusion controll of butynediol, and the most part of butanediol, the reaction products, accumulated in the plating solution not in the nickel deposits. Therefore, the decrease of current efficiency in bright nickel plating was considered to be caused by the reductive reaction of butynediol. Butynediol, the addition agent, which was electrochemically reduced on the electrode surface under the condition of diffusion controll behaved as a leveller.
