The process of forming a metallic nickel coating on a surface is called nickel plating or electrolytic nickel plating, regardless of the thickness of the coating or the base metal on which the electroplating is applied. The process of applying a nickel coating using a spray gun is also called nickel plating.
The reactions that occur 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 of the elements: 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 deposit 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 thick. This electroplated deposit 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.