When we use galvanized trivalent chromium black passivator to produce, sometimes the black color of the passivation film of the workpiece is uneven, and some do not form a film on the edge of the workpiece.At this time, the appearance of the workpiece is very bad, and the corrosion resistance is also very poor.So, what causes this?
Bigolly Technology made an analysis based on the field experience and the characteristics of the product galvanized trivalent chromium black passivator BZ-216. The uneven passivation film layer mainly has the following five reasons:
1. There are too many organic impurities in the electro-galvanizing bath.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, we should regularly treat the plating solution with activated carbon during production to reduce the impact of organic impurities.
2. The current density in 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, when black passivation is performed, 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 trivalent chromium black passivation agent, the thickness of the galvanized layer should be controlled to be more than 8μm as much as possible.
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, we should control the concentration, pH value and passivation time of the passivation solution within the process range during production.
5. The turning of the workpiece during the passivation process 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.Therefore, we should control the rolling strength of the workpiece during production.
Therefore, when we use galvanized trivalent chromium black passivator, the black unevenness of the passivation film of the workpiece should pay attention to the above 5 points to ensure the uniform blackness of the passivation film of the workpiece and effectively improve the performance quality of the coating.If you are interested in galvanized trivalent chromium black passivator, please contact Bigolly customer service, you can get free samples and detailed technical information!
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