Gold is the best material for all metallic coatings in the infrared range, but can only be used from a wavelength of 700 nanometers (nm). As 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 that does not tarnish and is therefore stable over the long term. A gold coating can therefore also be used without a protective layer, e.g. in FTIR spectroscopy. Areas of application for metallic coatings with gold are infrared mirrors (measurement technology), laser mirrors (low power applications) and protective coatings (corrosion protection).