Plastic Plating—Common Metal Impurities in Nickel Plating Solutions

Nickel plating electrolyte is very sensitive to impurities. When there are some metal impurities (the content of which is very small), the quality of nickel plating will deteriorate. Metal ions such as copper, iron, and zinc are the most common harmful metal impurities in nickel-plating solutions.

Iron is preferentially deposited on the cathode than a nickel in the electrolyte, which makes the coating brittle and easy to crack. The maximum content of iron in the nickel plating solution shall not be greater than 0.1 g/L. The precipitation potential of copper is low, so it is preferentially precipitated at the cathode so that the nickel layer is brown-black or gray-black. The maximum allowable content of copper is 0.02 g/l. The allowable content of zinc in the nickel plating solution is not more than 0.01 g/L. When the electrolyte contains a small amount of zinc, a bright coating will be produced on the edges and sharp corners of the plated parts. When the content is slightly larger, black streaks, spots, and scaly coatings are produced on the entire surface of the part.