Application of Ammonium Chloride in Electroplating Industry

  Ammonium chloride (NH4Cl) is a weak acid and weak base salt, and its aqueous solution is weakly acidic. During the plating process, the pH value of the plating solution will change due to various reactions. Ammonium chloride can play a cushioning role to a certain extent to prevent dramatic changes in the pH value of the bath. When the pH value of the bath increases, ammonium ion (NH4+) will combine with hydroxide ion (OH⁻) to form ammonia monohydrate (NHH · NH₂ O). When the pH value of the plating solution is reduced, ammonia monohydrate will release hydroxide ions, thereby stabilizing the pH value of the plating solution, which is very important to ensure the plating quality.

  During electroplating, ammonium chloride can form complexes with metal ions. For example, in the galvanizing process, it can form complexes with zinc ions. The formation of this complex can make the concentration of metal ions in the bath relatively stable. Because the presence of the complex can slow down the deposition rate of metal ions on the cathode, the coating is more uniform and fine.

  The presence of ammonium chloride can improve the binding force between coating and substrate. During electroplating, it can affect the deposition process of metal ions and make the crystallization of the coating more detailed and compact. For example, in some tin plating processes, adding an appropriate amount of ammonium chloride can improve the quality of the tin coating, reduce the porosity of the coating, and improve the corrosion resistance and decoration of the coating.

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