There are several different ways to cover a watch case with a protective or decorative material. Besides electroplating (also known as ElectroDeposition) there is Chemical Vapor Deposition and Physical Vapor Deposition. Both methods have many industrial applications.
PVD is the more popular method since it's less expensive and produces less waste. It uses less energy because it can be done at a lower temperature, but the quality of the coating is not quite as good as with CVD. However, PVD does have a much more equal distribution of the coating material than electroplating. The main types of PVD used in jewelry are evaporation and sputtering.
Both methods require ultrasonic cleansing of the object(s) to be coated before insertion into the chamber. As a comparison, the average electric current needed is 40 amps at 20 volts - much higher than electroplating. Both methods start by placing the item(s) inside a vacuum chamber with the surface coating material. In evaporation, the surface material is heated to a boil and evaporates. The vacuum state facilitates a uniform dispersal of the atoms causing the coating material to condense on all the surfaces in the chamber. In sputtering, an inert gas like argon is added to the compartment at low pressure. The gas is ionized by an RF power source, and then a stream of the gas is focused on the coating material which causes it to vaporize. Just like in the evaporation process, the vapor then condenses on all the surfaces of the chamber. Sputtering can usually be accomplished at a lower temperature than evaporation in most instances.
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