Zinc-nickel alloy coatings are widely used in many industrial applications due to their excellent corrosion resistance, high hardness and good decorative properties. Black passivation is a surface treatment process that provides better protection for zinc-nickel alloy coatings and gives them an attractive black surface. However, during the black passivation process, the surface of the coating is prone to coloration, which affects the appearance and corrosion protection. The coloration is caused by the non-uniformity of the passivate layer and is usually due to the following reasons:
1. The pH value of passivation solution is not suitable: the pH value of passivation solution has a significant impact on the quality of the film. Too high or too low pH can lead to film coloring. It is generally necessary to control the pH value of the passivation solution in the appropriate range to ensure the uniformity and stability of the film layer.
2. Improper passivation temperature: The temperature of the passivation treatment affects the passivation reaction rate and the growth of the film layer. If the temperature is too high or too low, it may lead to an increase in the inhomogeneity of the film layer, thus causing the phenomenon of coloration. Therefore, the strict control of passivation temperature is one of the key factors to avoid the appearance of coloration after black passivation of zinc-nickel alloy.
3. Failure to use the correct zinc-nickel passivate: Bigely zinc-nickel alloy black passivation solution helps to avoid color-flooding failures.
4. Poor pre-treatment: Improperly handled pre-treatment steps such as cleaning, degreasing and activation prior to plating can leave residual substances or cause inconsistencies in surface activity, affecting the uniformity of the passivated film and leading to color flooding. Therefore, close control of the pretreatment process is essential to obtain a good black passivation film.
5. Problems with the quality of the coating itself: Defects in the coating such as porosity, cracks, uneven alloy composition, etc. can cause color flooding during the subsequent passivation process. The quality of the coating is a prerequisite for a good passivation effect.
6. Contamination of the plating solution: The presence of impurities in the plating solution or an uneven content of metal ions, such as excess iron, copper or other metal ions, may affect the quality of the final passivated layer and lead to coloration. Regular analysis and maintenance of the plating solution, as well as the application of filtration systems are important measures to ensure the quality of the plating solution and avoid coloration.
In conclusion, the problem of color flooding during zinc-nickel alloys black passivation can be solved by controlling the process parameters, using Bigely zinc-nickel alloy black passivate, maintaining the plating solution and controlling the quality of pre-treatment, and ensuring the homogeneity of the plating layer itself.
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