Bright bluish white like silver and fragile mineral chromium are strongly resistant against air. It does not corrode, in other words rust in humid air. Therefore, most of the minerals having high potential of rusting are coated in a thin layer of chromium. Chromium is a mineral with rich ores in the nature. It was first discovered by French chemist Vauquelin in year 1797 at Siberia in a lead ore. Chromium is named after emerald, ruby and sapphire like beautiful colors of its compounds (Khroma in Greek means color). Chromium is generally available in crystal form in the nature. It is one of the first crystallized elements during hardening of the earth. Chromium ore is called chromite which means chrome rock. They are mostly available in thin crystal form inside the rocks. There are many known ores of chromium; of all these ores, emerald, ruby and sapphire are precious gems and therefore used in ornament making. However, the most common chromium ore is chromite. Chrome is primarily used to harden iron. Chromium-iron alloy is very hard and therefore useful in making abrasive tools such as file. Chromium-nickel alloy added iron provided very robust and flexible steel. They are used to make various machine parts, shields, bridges and electrical resistances. Chromium-wolfram alloys are much harder and used for production of bits used to machine particularly hard materials. Therefore, chromium compounds are widely used in the industry. These compunds have values of 2 3 5 6 7. Chromium 2 compounds are blue, chromium 3 compounds are green, chromium 6 and 7 compounds are yellow, orange and red. Chromium compounds are widely used in paint industry due to such qualities.

Chromium Characteristics

Physical and Chemical Properties

The most important ore of chromium is chromite mineral. Small amounts harden steel. Stainless steels containing chromium in the range of 10-26 are chromium-iron alloys. Natural chromium is available in four stable isotopes Chromium-50 (4.31%), Chromium-52 (86.76%), Chromium-53 (9.55%) and Chromium-54 (2.38%) mixture form. It dissolves slowly at room temperature in Hydrochloric acid and diluted sulfuric acid. It is not affected by aqua regia and fuming nitric acid.

Areas of Use for Chromium

Chromium ore is mainly used in metallurgy, chemistry, refractor and cast sand industries. Chrome is used in metallurgy industry as; ferrochromium, ferro-silico-chrome, chromium compounds, exothermic chromium additives, other chromium alloys and chromium metal. The most important use of chromium ore in metallurgy industry is ferrochromium production used to make stainless steel. Stainless steel is an important substance in metal and weapon industry. Chromium provides hardness, resistance against breakage and impacts, protection against corrosion and oxidation. Therefore, various alloys of chromium is used in bullet, submarine, ship, airplane, cannon and weapon support systems. Chromium chemicals are widely used in airplane and ship industries for its anti-corrosive properties; used in chemistry to make sodium bi-chromate, chromic acid and paint raw material, metal coating, leather tanning, paint materials (pigment), ceramics, polishing agents, catalysts, paints, organic synthetics, tinning agents, water treatment, drilling sludge and many other areas.

Chromium metal is used in high-performance alloys, Al, Ti, Cu alloys as well as alloys resistant against heat and electricity.

Super-alloys of chromium is used to make heat-resistant, high yield turbine engines. Having a high hardness grade and very resistant against corrosion, chromium is used in many areas from stainless steel industry (kitchenware, machine parts, etc.) to heavy equipment industry as well as coating and steel industries for such properties. Classified as a metallic ore, chromium is particularly used in metallurgy, chemistry, refractor and casting industry.

Obtaining Chromium

Depending on the type of product being processed, chromium ore can be classified in three categories, each being used for different purposes:

1 –Ores used in metallurgy,

2-Ores used in production of non-melting substances and anti-corrosive substances,

3-Ores intended for use in chemistry industry.

In order for an ore intended for metallurgy to be suitable to obtain pure chromium-iron alloy, it should contain minimum 48% Chrome oxide (Cr2O3), and should contain 1/3 chromium for iron. Chrome must be degraded in order to prepare chrome alloys.

Cr2O3 + 2Al 2Cr + Al2O3

2Cr2O3 + 3Si 4Cr + 3SiO2

For instance, oxygen should be combined with other elements such as carbon (coke) and destroyed at mine melting pits. Alloy named ferro-chromium which is an iron and chromium alloy is obtained in this manner. This alloy also contains some carbon. Although chromium is present in various minerals, the only resource to obtain chromium is chromite thanks to economical processing properties.