We all know that in the production process of using nickel plating brighteners, blackening of the low area coating of workpieces is a common fault phenomenon. So, what are the reasons and treatment methods for blackening of the nickel plating layer of workpieces in general?
Based on on-site experience and the characteristics of nickel plating brightener Ni-301, Bigley Technology has analyzed the following five situations:
1. The current is too low or the conductivity is poor. Sometimes during production, when the rectifier malfunctions or the anode rod has poor contact with the hanger, due to poor conductivity, the current obtained by the workpiece is too small to deposit a bright nickel coating, resulting in the overall darkening of the nickel coating. Therefore, we should regularly check the conductive circuit during the production process to ensure that the workpiece receives normal current.
2. Excessive brightener. Due to the addition of too much main brightener in the plating solution, it will affect the movement of nickel plating, and the plating solution will be more sensitive to impurities, leading to the phenomenon of low potential blackening. In addition, when the concentration of the main salt in the plating solution is low, the tolerance for the brightener will also be weak, and the brightener is prone to excessive use. Therefore, during our production process, we should control the total nickel concentration in the plating solution between 300-350g/L. When there is a slight excess of brightener, a softener should be added to smooth the amount of brightener, and impurities should be appropriately added to reduce the effect of brightener.
3. Excessive metal impurities in the plating solution. If metal impurities such as zinc and copper are accidentally introduced during the nickel plating process, such as impurities caused by poor washing, and accumulate to a certain amount, the low current area of the nickel plating layer on the workpiece is prone to blackening and darkening. When this phenomenon generally occurs, small current electrolysis method can be used to treat the plating solution, or Bigley's nickel plating impurity remover Ni-391 can be used to treat the metal impurities in the plating solution.
4. Excessive organic decomposition products. The various additives used in nickel plating production are all organic compounds. Long term supplementation of additives without treating the plating solution can easily lead to excessive accumulation of organic decomposition products in the plating solution, which can lead to darkening and blackening of the nickel plating layer. In the production process, activated carbon should be regularly used to adsorb a large amount of organic decomposition products in the plating solution, in order to achieve the goal of impurity removal.
5. The thickness of the base coating is not sufficient. Some zinc or aluminum alloy workpieces have certain requirements for the thickness and positioning of the cyanide plated copper layer when nickel plating, due to their chemical properties that are not resistant to acid and alkali. When the thickness of the copper layer is not enough, the nickel plating layer of the workpiece is prone to blackening. Therefore, before nickel plating, we should check the thickness and positioning performance of the cyanide copper plating layer, and proceed with nickel plating only after it is qualified.
Therefore, we should pay attention to the above 5 points in the production process of using nickel plating brighteners, which can effectively avoid the phenomenon of blackening in the low area of the nickel plating layer of the workpiece and improve production efficiency. If you are interested in nickel plating brighteners, please contact Bigley customer service for free samples and detailed technical information!
If you want to learn more about nickel plating, you can click to view the "Electroplating Encyclopedia".