Abstract
Many kinds of composition for zincate solution have been published. However, the authors presented the following equation in accordance with the results of their experiments.
X=αY2/3
where X: mol/l of ZnO or Zn (OH)2
Y: mol/l of KOH or NaOH
A zincate solution of which the value of α is less than 2, may be prepared. However, the solution of which α is more than 10, was generally stable. For instance, the zincate snlution (α=10), containing 10g/l of ZnO and 100g/l of NaOH, was desirable for electroplating bath.
Cathodic current efficiency of the zinc plating is very low, it is now prepared from cyanide zinc plating bath, from which NaOH is removed. However, the current efficiency gradually increased with the addition of NaOH to the bath and it finally reached nearly the maximum value at 80g/l of NaOH.
Cathode current efficiency of zincate bath, composed of 10g/l of ZnO and 100g/l of NaOH was still relatively high, but the deposit from it was very rough. However, the roughness of the deposit was improved when a small amount of NaCN was added to the bath.
As the results of these experiments, it can be concluded that the fundamental composition of cyanide zinc plating bath now prevailing is composed of zincate solution and NaCN may be assumed to be merely an addition agent.
