What is the Decorative Chromium Electroplating Process?

What is the Decorative Chromium Electroplating Process?

Decorative chromium electroplating is applied to metals and plastics. In decorative plating of metals, the base material generally is plated with layers of copper and nickel followed by a relatively thin layer of chromium to provide a bright surface with wear and tarnish resistance. Decorative plating is used for items such as automotive trim, metal furniture, bicycles, hand tools, and plumbing fixtures.

The decorative chromium electroplating process consists of pretreatment, alkaline cleaning, and acid dipping, which were described previously, followed by strike plating of copper, copper electroplating, nickel electroplating, and chromium electroplating. The copper strike plating step consists of applying a thin layer of copper in a copper cyanide solution to enhance the conductive properties of the base metal. Following the copper strike plate, the substrate is acid dipped again, and then electroplated with an undercoat of copper to improve corrosion resistance and cover defects. Either copper cyanide or acid copper solution is used in this step. The substrate then is plated with nickel in two layers (semi-bright nickel and bright nickel) to further improve corrosion resistance and activate the surface metal for chromium electroplating. Semi bright and bright nickel plating both use Watts plating baths. The final step in the process is the electroplating operation itself.

Decorative chromium plating requires shorter plating times and operates at lower current densities than does hard chromium plating. Some decorative chromium plating operations use fluoride catalysts instead of sulfuric acid because fluoride catalysts, such as fluosilicate or fluoborate, have been found to produce higher bath efficiencies.