What effect does sodium hydroxide have on the plating solution in our production process using alkaline zinc plating additives?
Bigolly Technology made an analysis based on the field experience and the characteristics of the product's alkaline zinc plating additives BZ-515,In the alkaline zinc plating solution, sodium hydroxide is a complexing agent for zinc, which can promote the dissolution of the anode and improve the conductivity of the plating solution, so it is very important to maintain a certain content.
With the increase of sodium hydroxide content in the bath, the dispersion ability and deep plating ability of the bath will become better, and the cathode current efficiency will decrease slightly.When the sodium hydroxide content is too high, the anodic dissolution will be accelerated, the zinc content will also increase, and the coating will be prone to blackening.In severe cases, the deep plating ability of the plating solution is significantly reduced, the current efficiency is reduced, and the passivation film is easily discolored.
When the sodium hydroxide content is high, the specific gravity of the plating solution increases, and a thick layer of agglomerates often appears in the plating solution.The added alkaline zinc plating additives will float on the surface and gather in the agglomerate, which will have no effect on the plating solution, and the plated workpiece will be black and not bright.
When the sodium hydroxide content is low, it is beneficial to reduce the hydrogen embrittlement of the elastic workpiece, because the current efficiency is increased, the hydrogen evolution is reduced, and the hydrogen permeation is weakened accordingly.But the sodium hydroxide content is too low, the current is not adjusted much, the coating will be rough if it is slightly larger, the deposition speed will be slow, the zinc will not be plated, or the coating will foam.At the same time, if the specific gravity of the bath is low, the added alkaline zinc plating additives will sink to the bottom, and even adding an excessive amount of alkaline zinc plating additives will have no effect.
Therefore, in the production process of using alkaline zinc plating additives, the influence of sodium hydroxide on the zincate plating solution is very large, and sufficient attention must be paid.