Effect of Chloride Ions on the Behavior of Saccharin, N-Methylsaccharin, and 2-Butyne-1,4-diol during Electrodeposition of Nickel from Acid Electrolytes

Rates of transformation of organic additives (saccharin, N-methylsaccharin, 2-butyne-1,4-diol) and accumulation of products of their cathodic reactions are studied during nickel electrodeposition from the chloride and Watts electrolytes. A large concentration of chloride ions accelerates the saccharine and N-methylsaccharin consumption due accelerated synthesis of o-toluenesulfamide, N-methyl-o-toluenesulfamide, and N-methylbenzylsultam, thus facilitating adsorption of additives on the nickel cathode via the carbonyl group. An inhibition of adsorption via the sulfonyl group is accompanied by a decrease in the accumulation of corresponding benzamides. An increase in the concentration of chloride ions in electrolytes containing 2-butyne-1,4-diol promotes accumulation of 2-buten-1,4-diol and inhibits hydrogenation of the double bond to a saturated bond. Differences in the behavior of the additives are due to (i) competition of chloride ions with the additives in the electrolyte or with their electroreduction products during adsorption on the nickel cathode, (ii) a change in the deposit potential, and (iii) a change in the concentration of inclusions in the deposits, which determine the catalytic activity of the cathode.