Chromite Chromium containing alloys are used in coins

INTRODUCTION

Chromium is the first member of group 6B. Chromium was discovered by the French scientist L. N. Vauquelin in 1797. The name chromium comes from the Latin word chroma, meaning color. Chromium compounds are used in the dye industry as a pigment. Chromium ions give the bright and attractive colors to precious stones such as ruby and sapphire. Pure chromium is grey in color, hard and bright like silver. The melting point is 1907°C, the boiling point is 2671°C and its density is 7.19 g/cm3 at room temperature.

OCCURENCE

The percentage of chromium is about 0.14% by mass in the earth's crust. It generally exists in volcanic stones and meteors. The most important mineral of chromium is chromite (FeO .Cr203), which has a brownish-black color. Moreover, its rarely found ore is chrocoite (PbCr04).

USES

In general, chromium metal is not used alone. Most chromium is used in the manufacture of stainless steel. It forms important alloys with iron, nickel, manganese and aluminum, such as ferro-chromium (60-70% Cr and 3040% iron) and nichrome (60%Ni, 25%Fe and 15%Cr), which has very high resistance to heat, and is used to build electrical furnaces.

Chromium is used for coating metals against corrosion. Chromium powder is used in the process of tanning, in dyes and in textiles.