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Basic knowledge of electroplating - electroplating solution

July 28, 2023

1. Primary salt
The main salt refers to the salt in the plating solution that can deposit the required coating metal on the cathode, and is used to provide metal ions. The concentration of the main salt in the plating solution must be in an appropriate range. The increase or decrease of the main salt concentration will have an impact on the electrodeposition process and the final coating structure when other conditions remain unchanged. For example, the concentration of the main salt increases, the current efficiency increases, the metal deposition speed increases, the coating grains are coarser, and the dispersion ability of the solution decreases.

2. Complexing agent
In some cases, if the metal ions of the main salt in the plating solution are simple ions, the grains of the coating will be coarse, so a plating solution with complex ions should be used. The method of obtaining complex ions is to add a complexing agent, that is, a substance that can complex metal ions of the main salt to form a complex. A complex is a "molecular compound" formed by the interaction of simple compounds. In the plating solution containing complexes, the main effect of electroplating is the relative content of the main salt and complexing agent, that is, the free amount of complexing agent, rather than the absolute content.

3. Additional salt
Additional salts are certain alkali metal or alkaline earth metal salts other than the main salt in electroplating, which are mainly used to improve the conductivity of the electroplating solution, and have no complexing effect on the metal ions in the main salt. Some additional salts can also improve the deep plating ability and dispersion ability of the plating solution, and produce a fine plating layer.

4. Buffer
A buffer is a substance used to stabilize the pH of a solution. Such substances are generally composed of weak acids and weak salts or weak bases and weak base salts, which can reduce the pH value of the solution when it encounters alkali or acid.

5. Anode activator
The substance in the plating solution that can promote the activation of the anode is called the anode activator. The role of the anode activator is to increase the current density at which the anode begins to passivate, thereby ensuring that the anode is in an activated state and can dissolve normally. When the content of the anode activator is insufficient, the anode dissolves abnormally, and the content of the main salt drops rapidly.


Affect the stability of the plating solution. In severe cases, electroplating cannot be carried out normally.

6. Additives
Additives refer to substances that can significantly improve the performance of the coating without significantly changing the conductivity of the coating. According to the role played in the bath, additives can be divided into: brighteners, leveling agents, and anti-fog agents.