Objects are metal coated for a number of reasons. In the industrial world, a metal coating can be used to protect the product from corrosion. For industrial tools, the metal film can act as both a vapor barrier to inhibit rust and as a friction reducer for moving parts. Friction reduction extends the useful life of a tool or other moving part.
In some cases, a product will receive a metal coating for appearance and luster. Many consumer products are given a shiny top coating to make them eye catching. A metal film may also be applied to interior electronic parts for electrical conductivity and protection. For outer surfaces, the film provides a more scratch resistant surface.
One method of applying a metal film is called physical vapor deposition. In this process, the product to be coated is placed in a vacuum chamber while the metallic coating substance is turned into a vapor. When in the chamber it attaches to the object and is condensed back to a thin film of metal. After cooling, a thin, hard, smooth surface is the result. Film material not attaching to the object is reclaimed and used again. Vaporizing and condensing are performed by a number of methods. The process is often referred to as sputtering or evaporative deposition.
Though not as common as electroplating, pvd technology has a number of advantages. Generally, PVD can be applied to a greater number of surfaces, including nonmetallic objects and products that have no electrical conductivity. These products include plastics and vinyl. A number of metals can be used for PVD applications,including chromium, titanium, aluminum and various alloys.
The metal layer applied is a very thin coating, measured in microns. The coating rarely affects the dimensions of the product. A Calo Tester is used to measure the thickness during the quality control process. Additional quality control steps test for scratch resistance, adhesion to the object and the hardness of the film. All are performed to ensure the coating will remain adhered to the underlying product and will withstand the wear and tear of its intended purposes.