Common problem

After the color zinc workpiece is passivated, the color of the hole is darker,Is this the improper operation of trivalent chromium color zinc passivator?

2022-06-02

    The trivalent chromium color zinc passivation workpieces we normally produce are uniform and bright color films, and sometimes the color of the passivated holes in the workpieces will be darker, showing yellowish green.Is this the improper operation of trivalent chromium color zinc passivator?

    Bigolly Technology made an analysis based on the field experience and the characteristics of the product's trivalent chromium color zinc passivator BZ-208,In fact, the main points of our operation in the production process mainly include the concentration, temperature, pH value and passivation time of the passivation solution.Once these details are not well controlled, there may be a phenomenon that the color of the hole is darker after the workpiece is passivated. The specific reasons are as follows:

    1. The concentration of passivation solution.The concentration of the passivation solution is higher, that is, the concentration of trivalent chromium ions is higher, the film formation speed of the galvanized layer is faster when the workpiece is passivated, and the color of the hole or edge position will be darker.When using trivalent chromium color zinc passivator, the concentration of trivalent chromium ions should be well controlled, and when the concentration is higher, it should be diluted proportionally.


    2. The temperature of the passivation solution.The temperature of the passivation solution is high, the film forming speed is relatively fast, and the color of the passivation film is relatively dark.During the production process, the temperature of the passivation solution should be controlled within the process range.

    3. The pH value of the passivation solution.The temperature of the passivation solution is low, the coloring speed is fast, and the color of the passivation film will be darker.During production, the pH value of the passivation solution should be controlled at 1.8~2.0, and try to ensure that the pH value does not fluctuate greatly.

    4. The workpiece passivation time is long.If the workpiece is passivated for a long time, more zinc coating will be dissolved, and the color of the passivation film will be darker.The passivation time of the workpiece should be controlled during production. If there is a workpiece in the passivation tank during shutdown, it should be taken out in time to avoid dissolving more zinc or iron, which will affect the passivation quality of the subsequent workpiece and the service life of the passivation solution.

    5. The pumping situation of the passivation solution.In the production process, if the pumping method of the passivation liquid is not appropriate (too large or too small), the passivation liquid will be uneven, and the color of the workpiece will be uneven after passivation, and the local color will be darker or lighter.Therefore, the pumping system of the passivation solution should be checked during production to ensure that the passivation solution is evenly pumped.

    Therefore, when using the trivalent chromium color zinc passivator, the operating instructions should be combined, and the concentration, temperature, pH value and passivation time of the passivation solution should be well controlled.Ensure that the passivation film after passivation of the workpiece is uniform and bright, and avoid the color of the hole being too dark.If you are interested in trivalent chromium color zinc passivator,please contact Bigolly customer service, you can get free samples and detailed technical information!   
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