When we use galvanized trivalent chromium black passivator, sometimes the passivation film of the workpiece is uneven in black, and some do not form a film on the edge of the workpiece, so the appearance of the workpiece is very unsightly, and the corrosion resistance is also very poor.So what is the reason for the uneven black color of the passivation film of the workpiece?
Bigolly Technology made an analysis based on the field experience and the characteristics of the product's galvanized trivalent chromium black passivator BZ-216,there are five main reasons for the uneven black color of the passivation film:
1. There are too many organic impurities in the plating solution for galvanizing.When there are too many organic impurities in the plating solution, the brightness of the plating layer will be uneven and the passivation effect will be affected.Therefore, the plating solution should be regularly treated with activated carbon during the production process to reduce the influence of organic impurities.
2. The current density during the electro-galvanizing process is too large.Excessive current density in the galvanizing process will cause the coating to be scorched at the edge, resulting in uneven color of the workpiece after black passivation treatment, and poor performance of the coating.
3. The thickness of the galvanized layer is too thin.When the thickness of the galvanized layer is too thin, during the black passivation treatment, the galvanized layer at the edge of the plated part will be exposed to the substrate due to dissolution, and the edge will not be black after passivation.Therefore, Bigolly recommends that when customers use black passivators, the thickness of the galvanized layer should be controlled to be more than 8μm.
4. The operating parameters of the black passivator are not properly controlled.If the concentration of the passivation solution is too low, the pH value is too low or the passivation time is too long, the black color of the passivation film will be uneven.Therefore, the concentration, pH value and passivation time of the passivation solution should be controlled within the process range.
5. During the passivation process, the turning of the workpiece is too violent.Especially in barrel plating production, excessive tumbling of the workpiece will cause the workpiece to have an uneven black appearance after passivation, so the tumbling strength of the workpiece should be well controlled.
Therefore, when we use galvanized trivalent chromium black passivator, we should pay attention to the above 5 points if the black color of the passive film of the workpiece is uneven, so as to ensure the uniform blackness of the passivation film and effectively improve the performance quality of the coating.If you are interested in galvanized trivalent chromium black passivator,please contact Bigolly customer service to get free samples and detailed technical information!
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