|Atomic mass||51.996 amu|
Chromium is a lustrous, malleable metal, silver-white with a bluish tinge. It was discovered in 1797 and like aluminum, it is very resistant to corrosion.
Chromium is not attacked by air or oxygen at ordinary temperatures. It forms a thin, tough, protective film of oxide.
The chief ore is chromite, FeCr2O4, which is reacted with coke or coal in a furnace to produce ferrochrome, a Cr-Fe alloy used directly in steelmaking. Ferrochrome is used in making chromium steels. Stainless steel contains 14 to 18% chromium and improves hardness and resistance to rusting. Chromium-vanadium steel contains 1 to 10 % chromium together with about 0.15 % vanadium. These steels are very strong and are used to make axles that must withstand constant strain as well as frequent shock and vibration.
- Electroplated chromium, as used on car bumpers door handles, tableware and ornaments retains its bright surface for many years.
- The oxides Cr2O3 (green) and CrO3 (red-orange) are used as pigments in paint.
- Chromium is essential to glucose metabolism. In 1959, chromium is determined to be an essential dietary trace element in animals. Chromium deficiency has been observed among children with severe protein deficiency in undeveloped countries. Meat, beer, and unrefined wheat flour are dietary sources of chromium.