Some customers inquired that in the production process of using black zinc passivator, the appearance of the workpiece passivation film is obviously black and shiny, but soon after drying, the passivation film will appear the phenomenon of small white spots, what is the reason for this?
Bigely Technology made an analysis based on the field experience and the characteristics of the product trivalent chromium black zinc passivator BZ-217, this phenomenon is mainly due to the poor quality of the passivation film of the workpiece, resulting in the passivation film is easy to be corroded and the phenomenon of white rust, i.e., the small white spots. Generally this phenomenon is mainly due to the following four kinds of reasons:
1、The thickness of the galvanized layer is too thin. After the workpiece is black passivated, the galvanized layer is too thin in some positions, so that the workpiece is easily corroded and white rust occurs in the storage process.
2, passivation solution due to improper operation or more impurities lead to poor quality of the workpiece passivation film. We are in the production process due to passivation solution concentration, pH, temperature and passivation time and other process parameters are not operating properly, or use a longer period of time after the passivation solution in the zinc, iron ions and other high content, will affect the quality of the workpiece passivation film, so that the workpiece's corrosion resistance is poor.
3. The black zinc passivator used is of poor quality. Some black zinc passivators due to immature formulations or impure raw materials and other reasons, resulting in the workpiece passivation failed to obtain a dense passivation film, thus affecting the corrosion resistance of the passivation film. It is recommended to use a big brand of black zinc passivator, such as Bigely's BZ-217, which ensures good corrosion resistance of the passivate film on the workpiece.
4. Inadequate drying of the workpiece after passivation. After the workpiece is black zinc passivated, if the drying temperature of the workpiece is low or the drying time is not long enough, it will lead to poor bonding and corrosion resistance of the workpiece.
Therefore, we should pay attention to these 4 points in the production process of using trivalent chromium black zinc passivator, and with the use of sealers, can effectively improve the corrosion resistance of the workpiece passivation film, thus avoiding the appearance of small white spots phenomenon, reduce the occurrence of failures. If you are interested in trivalent chromium black zinc passivator, please contact Bigely customer service for free samples and detailed technical information!
