Uses of Chromium

Chromium is a chemical element (atomic number 24), which belongs to the category of transition metals. This hard, steel-gray colored bright metal is placed in group 6 of the periodic table and is represented by the chemical symbol Cr. It was discovered by Louis Nicholas Vauquelin, in the mineral crocoite, which consists of lead chromate. The name chromium is derived from the Greek word chroma, which means color, owing to the different colors produced by its compounds. Cromium is the 21st most abundant element found on the Earth's crust. However, it never occurs as a free metal and is extracted from the mines as chromite ore. Chromium occurs in many oxidative states like +1, +2, +3, +4, +5, +6, out of which +2, +3 and +6 are most common, while +1, +4 and +5 are the rare oxidation states.

Uses of Chromium

Chromium has found a wide range of applications, mainly due to its hardness and resistance to corrosion. It is also known for its remarkable magnetic property. It is mainly used in the manufacture of stainless steel, along with nickel, as it prevents corrosion and discoloration of steel. Today, chromium is a very important alloying material for steel.

Acidic chromate or dichromate solutions are also used for surface coating. This is usually done with the help of electroplating technique, in which a thin layer of chromium is usually deposited on the surface of metals. However, for imparting wear resistance quality, a thick layer is required to be deposited. Another method of doing this is the chromate conversion coating process, through which chromates are used to deposit a protective layer on certain metals like aluminum (Al), cadmium (Cd), zinc (Zn), silver, magnesium (Mg), etc.

Salts of chromium are used for their toxic properties in preserving wood from decay and damage caused by fungi, insects, termites, etc. Chromium (III) salts are also used in leather tanning. The high melting point and resistance to heat makes chromite and chromium oxide an ideal refractory material. They have found applications in blast furnaces, cement kilns and metal casting. Besides, many compounds of chromium are also used as catalysts. Chromium (IV) oxide is used to produce magnetic tapes, which are used in audio tapes and cassettes.

Chromium is also used as a pigment. Chrome yellow, made of lead chromate was widely used as a pigment in the past, but due to environmental issues, its use has significantly declined as it contains lead, which is a toxic material. Other pigments of chromium include chrome red, chrome oxide green and chrome green, which is a mixture of chrome yellow and Prussian blue. Chromium oxide is used for imparting greenish color to glass. Besides, emeralds also owe their green tint to the effect of chromium. Chromium oxide is also used in manufacturing synthetic rubies.

Chromium (III) or trivalent chromium is required in the human body, but in very small amounts. It is mainly required for carrying out lipid and sugar metabolism. Nowadays, chromium is used in many dietary supplements claiming to have several health benefits. But, some compounds of chromium can be harmful to health and should be avoided. For example, hexavalent chromium or Chromium (VI) is known as a toxic and mutagenic (causing mutation) substance, while chromium (IV) is known for its carcinogenic or cancer causing properties. Chromate salts have also been found to induce allergic reactions in some individuals. Due to these health and environmental issues, restrictions have been imposed on the use of certain chromium compounds in many countries.