Reasons And Solution Strategies For Misting in Potassium Chloride Zinc Plating Process

In the potassium chloride zinc plating process, if the lead impurities in the plating solution exceed a certain proportion, it will cause the coating to become foggy. What are the specific reasons? How should we solve it?
The hazards of lead impurities
Trace amounts of lead ions can also cause fogging of the coating. When producing potassium chloride zinc plating process, we do not often encounter lead impurities. There are two sources of lead impurities: one is zinc plate with insufficient purity, and the other is zinc chloride with insufficient purity.
Compared to copper impurities, lead impurities have a greater impact. When the lead content in the plating solution exceeds 5 mg/L, the passivation coating becomes foggy after passivation, resulting in poor gloss of the passivation film. The passivation film quickly changes color. When the lead content exceeds 10 mg/L, the plating solution's coverage ability decreases. In severe cases, the plating layer does not deposit during barrel plating, and it appears to have a coating. However, once diluted nitric acid is exposed, it quickly becomes exposed.
The zinc plating solution contaminated by lead impurities makes it difficult to obtain a blue white film on the coating after plating; The colored passivation film is prone to discoloration. Lead impurities seriously reduce current efficiency, resulting in slow coating and thin coating.
How do we need to solve it?
The lead impurity content in potassium chloride zinc plating solution needs to be controlled below 5 mg/L. To deal with lead impurities, there are usually two methods:
① Electrolytic method
② Treat with zinc powder
However, these two methods are more difficult to handle than copper impurities. Therefore, we must pay attention to product quality during the procurement, replacement of zinc plates, and addition of zinc chloride.