Chromium is a very hard, brittle, gray metal, which is sometimes
referred to as Siberian red lead. It does not rust easily and becomes shiny and
bright when it is polished. The shiny trim on our automobile bumpers and
door handles is usually electroplated chromium.
Most chromium comes from something called chromite which is
a mixture of chromium , iron, and oxygen. Chromite is a common rather
ordinary black mineral that no one really noticed until more recent times.
Nearly all the world's supply of chromite comes from Zimbabwe, Russia,
Turkey, South Africa, Cuba, and the Philippines. The United States imports
almost all its chromite.
Chromium is added to other metals to make them harder and
more resistant to chemicals. Small quantities mixed with steel make the metal
stainless. Stainless steel is used to make cutlery and kitchen equipment
because it does not rust easily and takes a mirror-like polish.
contains about 13 percent chromium and 0.3 percent carbon.
The hardness of steel can be increased by adding small
quantities of chromium to it. Chromium steel alloys (mixtures containing one
or more metals) are used to make armor plating for tanks and warships. They
are also used for ball bearings and the hard cutting edges of high-speed
Nickel is highly resistant to electric current and is often added to
chromium steels to make them easier to work. For example, stainless steel
sinks can be pressed out from flat sheets of steel that can contain 18 percent
chomium and 8 percent nickel.
When nickel is mixed with chromium, the resulting metal can
stand very high temperatures without corroding. For example, the heating
elements of toasters can be made from an alloy that is 80 percent nickel and
20 percent chromium. This metal operates at a temperature...