For general surface plating, please refer to this technical Tips.
"What is surface treatment? Explaining the main types and the role of power supply"

In this web page, we will introduce a method called ion plating.

This plating process technology, called ion plating, is used in the U.S. space program.
There are two major methods of plating process: wet plating and dry plating (vacuum plating), and ion plating belongs to the latter.
In the process, the material is evaporated or sublimated in a vacuum, and the evaporated particles are passed through the plasma.
Then, the positively charged object is attracted to a negatively charged object and deposited there.
Finally, the desired film is formed.