Gold is the best material for all metallic coatings in the infrared range, however, it can only be used from a wavelength of 700 nanometers (nm). Since a gold coating is soft, it scratches easily. For this reason, the gold coating should be provided with a dielectric coating.
Gold is a precious metal and therefore does not tarnish, and is therefore stable over the long term. A gold coating can therefore also be used without a protective layer, for example in FTIR spectroscopy. Applications of metallic coatings with gold are infrared mirrors (measurement technology), laser mirrors (low power applications) as well as protective coatings (corrosion protection).