In the alkaline galvanizing process, sometimes after the product is zinc-plated, it is passivated and yellowed by trivalent chromium blue zinc water, which affects the product quality and is not accepted by customers. So how should we solve this problem?
Author: Marisa
In the alkaline galvanizing process, sometimes after the product is zinc-plated, it is passivated and yellowed by trivalent chromium blue zinc water, which affects the product quality and is not accepted by customers. So how should we solve this problem?
Based on on-site experience and product characteristics, we made the following analysis:
1. The pH value of the passivation solution is low. If the pH is low, the product will passivate faster, and the pH of the passivation solution should be adjusted to within the normal range.
2. The concentration of the passivation solution is too high. If the concentration is too high, the product will passivate faster. You should stop adding the stock solution, drain part of the passivation solution, and add water to dilute it to a concentration within the normal range.
3. The product passivation time is too long. If the passivation time is too long, the product will passivate faster. The passivation time should be reasonably shortened according to the product requirements.
4. The temperature of the passivation solution is high. The temperature is high. The product passivates faster, and the temperature should be lowered to within the normal range.
5. The iron ion content in the passivation solution is high. The high iron ion content makes the product easy to turn yellow during passivation.
Part of the passivation solution should be drained and the original solution should be replenished to control the iron ion content in the passivation solution. Therefore, if the trivalent chromium blue zinc water turns yellow during passivation, the pH value, concentration, temperature, passivation time and iron ion content of the passivation solution should be checked.