In the production process of using galvanized trivalent chromium multicolored passivation solution, how do we keep the working fluid stable and effectively extend the service life?
Bigley Technology has analyzed the characteristics of trivalent chromium multicolored passivation solution BZ-208 based on field experience and products. Generally, the following 7 points should be paid attention to:
1. Replenishment of passivation solution. Due to the reaction consumption and carry-out loss of the workpiece during the production process, the concentration of the working fluid is constantly decreasing. Therefore, the concentration of the working fluid should be periodically analyzed during production and supplemented in time.
2. Maintain uniform air stirring. Generally, the multicolored passivation liquid requires strong and uniform air stirring, which can ensure the stability of the working liquid, and can ensure that the workpiece can obtain a uniform and dense passivation film with good corrosion resistance.
3. Control of pH value of working fluid. Generally, in the production process, the pH value of the passivation solution will gradually rise due to the passivation reaction of zinc, the introduction of water and the withdrawal of the working fluid. When the pH value of the working fluid is too high, the performance of the passivation film will be slower, which will affect the production schedule. Therefore, we should determine in time during production, and use nitric acid solution to control the pH value of the passivation solution within the range of 2.0-2.5.
4. Control of passivation time. Generally, the passivation time of the workpiece is between 40-60 seconds, and if the pH value of the passivation liquid is controlled at 1.8-2.0, after the working liquid is aged, the passivation time of the workpiece can be shortened by 30-45 seconds.
5. Baking and aging. After the workpiece is passivated and cleaned with cold and hot water, it needs to be baked and aged. If the baking temperature of the workpiece is too low or the time is too short, the moisture on the surface of the workpiece cannot be evaporated to dryness, and the passive film of the workpiece is prone to yellowing and poor corrosion resistance; and when the baking temperature is too high, the passive film of the workpiece is prone to appear Cracks and poor corrosion resistance. Therefore, the general baking temperature of the workpiece is 60-80℃, and the time is 10-25 minutes.
6. Aging update of working fluid. As the production progresses, the concentration of zinc and iron ions in the working fluid will continue to increase. When the content reaches a certain limit, it will seriously affect the appearance, color and corrosion resistance of the passive film of the workpiece. Therefore, Bigley advises customers: When the iron ion content in the working fluid reaches 30ppm and the zinc ion content reaches 5g/L, the working fluid needs to be aged, that is, drain 1/3 of the working fluid at the bottom of the tank, and then add Zinc passivation solution.
7. Since the trivalent chromium passivation film is easy to be scratched and bruised, care should be taken during the production process to avoid bruising, so as to ensure the good corrosion resistance of the passivation film of the workpiece.
Therefore, we need to pay attention to the above 7 points in the production process of using zinc-plated trivalent chromium multicolored passivation agent to effectively reduce the failure rate of production, reduce the frequency of adjusting the working fluid, and maintain the temperature of the working fluid, thereby effectively extending the work The service life of the liquid. If you are interested in zinc trivalent chromium multicolored passivation agent, please contact Bigley customer service to get free samples and detailed technical information!