Chromium is a mineral. It is called an “essential trace element” because very small amounts of chromium are necessary for human health. There are two forms of chromium. Trivalent chromium is found in foods and supplements and is safe for humans. The other form, hexavalent chromium, is a known toxin that can cause skin problems and lung cancer. Only trivalent chromium is discussed here.
Chromium is used for chromium deficiency. It is also used for diabetes, high cholesterol, a hormonal disorder that causes enlarged ovaries with cysts (polycystic ovary syndrome or PCOS), and many other conditions, but there is no good scientific evidence to support most of these uses. But In this article, we Discuss chromium as metal and its properties and uses.
What is Chromium Metal ?
Chromium is a chemical element with the symbol Cr and the atomic number 24. It is the first element of group 6. It is a steel-gray, shiny, hard, and brittle transition metal. Chromium is the main additive in stainless steel, which gives anti-corrosive properties.
Chrome is also valued as a metal that can be polished to a mirror finish while resisting tarnishing. Polished chrome reflects almost 70% of the visible spectrum and almost 90% of the infrared light.
Chrome metal is valued for its high corrosion resistance and hardness. An important development in steel production was the discovery that steel can be made highly resistant to corrosion and discoloration by adding metallic chromium to form stainless steel. Stainless steel and chrome plating together make up 85% of commercial use.
The industrial production of chromium takes place from chromite ore (mostly FeCr2O4) to ferrochrome, an iron-chromium alloy, through aluminothermic or silicothermic reactions.
Ferrochrome is then used to make alloys such as stainless steel. Pure chrome metal is made by a different process: roasting and leaching chromite to separate it from iron, followed by reduction with carbon and then with aluminum.
|Group||6||Melting point||1907°C, 3465°F, 2180 K|
|Period||4||Boiling point||2671°C, 4840°F, 2944 K|
|Block||d||Density (g cm−3)||7.15|
|Atomic number||24||Relative atomic mass||51.996|
|State at 20°C||Solid||Key isotopes||52Cr|
|Electron configuration||[Ar] 3d54s1||CAS number||7440-47-3|
Who Discovered Chromium?
Chromium was discovered (1797) by the French chemist Nicolas-Louis Vauquelin and isolated as the metal a year later; it was named for its multicolored compounds. He produced chromium oxide (CrO3) by mixing crocoite with hydrochloric acid (HCl).
Although he believed a method for isolating chromium didn’t yet exist, Vauquelin was pleasantly surprised in 1798 to discover that he was able to obtain metallic chromium by simply heating chromium oxide in a charcoal oven. Today, chromium is primarily obtained by heating the mineral chromite (FeCr2O4) in the presence of aluminum or silicon.
Properties of Chromium
Chromium is a lustrous, brittle, hard metal. Its color is silver-gray and it can be highly polished. It does not tarnish in the air, when heated it borns and forms green chromic oxide. Chromium is unstable in oxygen, it immediately produces a thin oxide layer that is impermeable to oxygen and protects the metal below.
Chromium has a melting point of 1857+/-20°C, a boiling point of 2672°C, a specific gravity of 7.18 to 7.20 (20°C), with valences usually 2, 3, or 6. The metal is a lustrous steel-gray color that takes a high polish. It is hard and resistant to corrosion.
Chromium has a high melting point, stable crystalline structure, and moderate thermal expansion. All chromium compounds are colored. Chromium compounds are toxic.
Chromium metal is a chemical element by the symbol Cr and atomic number 24. It is the first element in group 6. Chromium is a fairly active metal. It does not react with water but reacts with most acids. It combines with oxygen at room temperature to form chromium oxide (Cr2O3). Chromium oxide forms a thin layer on the metal surface, protecting it from further corrosion.
Chromium (Cr) is a brilliant, hard, refractory metal that melts at 1,857 °C (3,375 °F) and boils at 2,672 °C (4,842 °F). In the pure state, it is resistant to ordinary corrosion, resulting in its application as an electroplated protective coating for other metals. It dissolves in nonoxidizing mineral acids but not in aqua regia or nitric acid, which passivate the metal.
Because chromium and chromium-rich alloys are brittle at room temperature, they have limited application. By far the largest consumption is as an alloying addition to iron. In amounts varying from 10 to 26 percent, chromium imparts corrosion resistance to steel; it is also used to improve hardenability, wear-resistance, and high-temperature strength.
As the mineral chromite, chromium is employed extensively as a refractory material. Other chromium chemicals are used as pigments and tanning agents.
Uses of Chromium
Chromium plating can be used to give a polished mirror finish to steel. Chromium-plated car and lorry parts, such as bumpers, were once very common. It is also possible to chromium plate plastics, which are often used in bathroom fittings.
About 90% of all leather is tanned using chrome. However, the waste effluent is toxic so alternatives are being investigated. Chromium compounds are used as industrial catalysts and pigments (in bright green, yellow, red, and orange colors). Rubies get their red color from chromium, and glass treated with chromium has an emerald green color.
Chromium Element and its uses
Chromium elements have many different uses. Some include:
- chromic fluoride (CrF 3): printing, dyeing, and mothproofing woolen cloth
- chromic oxide (Cr 2 O 3): a green pigment (coloring agent) in paint, asphalt roofing, and ceramic materials; refractory bricks; abrasive
- chromic sulfate (Cr 2 (SO 4) 3): a green pigment in paint, ceramics, glazes, varnishes, and inks; chrome plating
- chromium boride (CrB): refractory; a high-temperature electrical conductor
- chromium dioxide (CrO 2): covering for magnetic tapes (“chromium” tapes)
- chromium hexacarbonyl (Cr (CO) 6): catalyst; gasoline additive
What is chromium metal used for?
A hard, silvery metal with a blue tinge. Chromium is used to harden steel, to manufacture stainless steel (named as it won’t rust), and produce several alloys. Chromium plating can be used to give a polished mirror finish to steel.
Is chromium a cheap metal?
As a shiny element, chromium is almost unbeatable: It’s cheap, easy to electroplate, does not corrode, and of course, it’s very shiny. Silver is shiny too, but it tarnishes quickly.
How strong is chromium metal?
With a rating of 8.5 on the Moh’s hardness scale, chromium is the hardest metal on the planet (easily outclassing titanium, which is rated at a mere 6.
Is chromium a toxic metal?
Chromium as the pure metal has no adverse effect. The little toxic effect is attributed to trivalent chromium when present in very large quantities. Both acute and chronic toxicity of chromium is mainly caused by hexavalent compounds.
Is chromium toxic to humans?
Human studies have clearly established that inhaled chromium (VI) is a human carcinogen, resulting in an increased risk of lung cancer. Animal studies have shown chromium (VI) to cause lung tumors via inhalation exposure.
Is chromium a good metal?
Stainless steel and chrome plating (electroplating with chromium) together comprise 85% of the commercial use. Chromium is also highly valued as a metal that is able to be highly polished while resisting tarnishing.
Is chromium natural or synthetic?
It is naturally found in compounds in the earth’s crust. However, consuming high levels of chromium in polluted drinking water or inhaling fumes of the heated element can cause ulcers, cancer, and other health problems.
What are 5 uses of chromium?
The Uses of Chromium in the Chemical Industry. It is mainly used in electroplating, tanning, printing, and dyeing, medicine, fuel, catalysts, oxidants, matches, and metal corrosion inhibitors. At the same time, metallic chromium has become one of the most important electroplated metals.
Can chromium be forged?
Pure chromium (like many other non-ferrous metals) work-hardens. This makes it unsuitable for forging as the resulting blade would be very brittle.
What’s bad about chromium?
Chromium VI is the most dangerous form of chromium and may cause health problems including allergic reactions, skin rash, nose irritations, and nosebleeds, ulsers, weakened immune system, genetic material alteration, kidney, and liver damage, and may even go as far as the death of the individual.
Is chromium rust toxic?
In fact, on a gram-for-gram basis, chromium is not considered particularly toxic as compared to other metals, even by ingestion.
Is chromium in stainless steel toxic?
Toxicological studies show that oral doses of nickel and chromium can cause cutaneous adverse reactions such as dermatitis. Additional dietary sources, such as leaching from stainless steel cookware during food preparation, are not well characterized.
Is chromium corrosion resistant?
Although chromium corrodes in a similar manner, its oxide, Cr2O3 forms a hard surface layer preventing oxygen from reacting with iron. More corrosion-resistant stainless steels such as those used in building construction contain molybdenum as well as chromium.
Why does chromium prevent rust?
The chromium combines with the oxygen before the iron is able to which forms a chromium oxide layer. This layer is very corrosion resistant which prevents rust formation and protects the underlying metal.
What kind of metal is chromium?
Chromium (Cr), a chemical element of Group 6 (VIb) of the periodic table, a hard steel-gray metal that takes a high polish and is used in alloys to increase strength and corrosion resistance.
Is chromium a good conductor of electricity?
Chromium. Not a very good electrical conductor by any means, but it does have its uses in this field. Chromium Boride (CrB) is used as a high-temperature electrical conductor. There are many other uses for this metal.
How do you make chromium?
Pure chromium is produced either by the thermal reduction of Cr2O3 with aluminum or by the electrolysis of trivalent chromium solutions. The aluminothermic process begins with the roasting of fine ore, soda, and lime in air at 1,100 °C (2,000 °F).
Why is chromium used in stainless steel?
Chromium is critical in the manufacturing of stainless steel. Most stainless steel contains about 18 percent chromium; it is what hardens and toughens steel and increases its resistance to corrosion, especially at high temperatures. Chromium-containing pigments find their way into a variety of beauty products.