How to deal with gray-black or black streaks on workpiece coating when using nickel plating brightener

How to deal with gray-black or black streaks on workpiece coating when using nickel plating brightener

Tue Aug 16 17:47:44 CST 2022

    When we use nickel plating brightener to produce, sometimes the coating of the workpiece will have gray-black or black stripes, which will seriously affect the appearance of the product.So how should the workpiece be dealt with when this phenomenon occurs?

    Bigolly Technology made an analysis based on the field experience and the characteristics of the product's nickel plating brightener Ni-301,When the content of Pb2+, Zn2+, Cu2+, NO3- plasma impurities in the plating solution exceeds the allowable range, the nickel-plated layer of the workpiece will appear embrittlement, gray-black or black stripes.

    When the content of Pb2+ exceeds 7mg/L, the concave part of the workpiece and the lead wire that binds the workpiece not only have no coating, but also appear gray-black.When the content of Zn2+ exceeds 0.02g/L, the coating will become brittle and black streaks will appear.When the Cu2+ content exceeds 0.03g/L, a dark black rough coating will appear in the low current density area.When the NO3- content is 0.2g/L, the cathode current efficiency will be significantly reduced, and the coating will be black.

    The impurities of Zn2+ and Cu2+ can be removed by electrolysis, that is, an electrolytic plate is used as the cathode, and the electrolytic treatment is carried out with a small current of 0.1~0.5A/dm2 under the condition of stirring.It can also be removed with Bigolly Technology's Ni-391 impurity remover.

    The removal of Pb2+ impurities requires a pH value of 6.2, the plating solution will generate Pb(OH)2 precipitation, filter the plating solution to remove Pb2+ impurities, and then use 0.1A/dm2 low current electrolytic plating solution for 2 hours, Pb2+ impurities are basically removed.

    The treatment method of NO3- impurity is:Adjust the pH value of the plating solution at 1.0~2.0, maintain the temperature of the plating solution at 60~70°C, and perform electrolysis with 1~2A/dm2 at the cathode current density, so that NO3- is reduced to NH3 at the cathode and escapes.Then gradually reduce the current density to 0.2A/dm2, and electrolyze until the plating solution is normal.

    Therefore, in the production process of using nickel plating brightener, when gray-black or black stripes appear on the workpiece, we should check whether the impurity content in the plating solution exceeds the allowable range, and deal with the plating solution in time to reduce the loss caused by failure.If you are interested in nickel plating brightener,please contact Bigolly customer service to get free samples and detailed technical information!

    If you want to know more about nickel plating, you can check "Electroplating encyclopedia".