Vacuum metalizing is a process in which thin coatings of metal compounds are deposited on workpiece surfaces in a vacuum chamber. Parts are normally pre-coated before metalizing and a protective layer is applied. Electronic components such as capacitors, integrated circuits, contacts, and photoconductors utilize vacuum coatings. Vacuum metallization is used for bright and lustrous effects in products such as automobile light reflectors and other applications such as optical glasses.
Vacuum metalization applications (Image source)
Typical examples of coating on different substrates.
Aluminium is widely used for vacuum coating. It vaporizes easily at less vacuum pressure. Many other metals can be used for vacuum coating depending upon their volatility and vacuum coating ability.