The process of forming a metallic nickel coating on a surface is called nickel plating or electrolytic nickel plating, regardless of the coating thickness or the base metal on which the electroplating is performed. The process by which nickel is applied using a spray gun is also called nickel plating.
The reactions that take place during the electrolytic process are:
In industry, it is very common to use multiple coatings. In the case of copper-nickel-chromium coatings on ferrous materials, specific thicknesses are used for each element: for copper, from 10 μm to 20 μm; for nickel, from 5 μm to 20 μm; while chromium is always 0.3 μm. This electroplating process is widely used in the metalworking industry, as it provides a finish that is highly resistant to corrosion and very aesthetically pleasing. When the base metal is zinc, nickel is deposited at a thickness of 8 μm to 35 μm, chromium at 0.3 μm to 0.8 μm, and copper at 8 μm to 10 μm. In the case of zamak (a zinc alloy), copper can be replaced by brass or bronze.
When a nickel-chromium electroplated coating is applied—typically to copper and its alloys—the thickness of the nickel deposit ranges from 4 μm to 16 μm, and the chromium deposit is 0.3 μm. This electroplated coating is suitable for moderately corrosive environments.
For nickel coatings on copper substrates, Ni thicknesses ranging from 3 μm to 6 μm are used, while for ferrous materials, the thicknesses range from 3 μm to 5 μm.
Source: FELIPE DÍAZ DEL CASTILLO R.