Chromium Information
Scroll Down To Download
Chromium Element
Chromium is a chemical element
with the symbol Cr and atomic number 24. It is the first element in group 6. It
is a steely-grey, lustrous, hard and brittle transition metal.[4] Chromium is
the main additive in stainless steel, to which it adds anti-corrosive
properties. Chromium is also highly valued as a metal that is able to be highly
polished while resisting tarnishing. Polished chromium reflects almost 70% of
the visible spectrum, with almost 90% of infrared light being reflected.[5] The
name of the element is derived from the Greek word χρῶμα, chrōma, meaning color,[6] because many
chromium compounds are intensely colored.
Chromium is a relatively
abundant element in Earth’s crust; the free metal is never found in nature.
Most ores consist of the mineral chromite, the ideal formula of which is
FeCr2O4. It is widely dispersed in natural deposits, which are usually
contaminated with oxygen, magnesium, aluminum, and silica; their chromium
content varies from 42 to 56 percent. One of the chief uses of chromium is in
ferrous alloys, for which the pure metal is not required. Accordingly, chromite
is often reduced with carbon in a furnace, producing the alloy ferrochromium,
which contains iron and chromium in an atom ratio of approximately 1 to 2.
Ferrochromium alloy is
commercially produced from chromite by silicothermic or aluminothermic
reactions and chromium metal by roasting and leaching processes followed by
reduction with carbon and then aluminium. Chromium metal is of high value for
its high corrosion resistance and hardness. A major development in steel
production was the discovery that steel could be made highly resistant to
corrosion and discoloration by adding metallic chromium to form stainless
steel. Stainless steel and chrome plating (electroplating with chromium)
together comprise 85% of the commercial use.
In the United States, trivalent
chromium (Cr(III)) ion is considered an essential nutrient in humans for
insulin, sugar and lipid metabolism.[7] However, in 2014, the European Food
Safety Authority, acting for the European Union, concluded that there was not
sufficient evidence for chromium to be recognized as essential.[8]
While chromium metal and
Cr(III) ions are not considered toxic, hexavalent chromium (Cr(VI)) is both
toxic and carcinogenic. Abandoned chromium production sites often require
environmental cleanup.[9]
Movies ColdStar is The Best
Website/Platform For Hollywood HD Movies. We Provide Direct Download Links For
Fast And Secure Downloading. Just Click On Download Button.
Comments
Post a Comment