Gold

The high cost of gold in combination with its susceptibility to corrosion from halogens severely limits its use for corrosion properties. Gold is readily attacked by hot mixtures of HNO3 and H2SO4, aqua regia, hydrogen cyanide, mixtures of HBr, HCl, HI, and HNO3. Gold has been used as an autoclave lining for handling phosphate mixtures up to 500ºC and in the chemical industry for lining equipment used in hydrochlorinations and hydrofluorinations.