Abstract
The effects of substituents and their positions in pyridine rings on the properties of electroplated nickels were studied. The crystal microstructure, brightness, cracks, and hardness of deposits obtained from Watts bath containing 24×10-3mol/l of saccharin and 10-3 or 10-4 mol/l of pyridine derivatives were explained. When the electrolysis was carried out at a current density of 2 Amp/dm2 in the presence of 10-4mol/l of pyridine derivatives, the following results were obtained: The deposit obtained from the addition of 3-aminopyridine or 3-cyanopyridine was laminar and bright, while that obtained from the addition of 3-methylpyridine, 3-hydroxypyridine, or 3-pyridine carboxylic acid was columnar and dull. The deposit obtained from the addition of 3-pyridine carbaldehyde was granular and semi-bright. The decreasing order of hardness of the deposits obtained from the addition of these 3-substituted pyridines was as follows: cyano>amino>aldehyde>hydroxyl>methyl>carboxyl. The microstructures and brightnesses of the deposits obtained from the addition of 2-, 3-, and 4-aminopyridines were similar one another. The hardness of the deposits obtained from the addition of these aminopyridines was arranged in decreasing order of 2-≥3->4-. No cracks were observed in the deposits mentioned above.
