Technical use black chromium coating is typical optical equipment and the like, as anti- reflective surface. The surface of the black chromium mainly consist chromium oxide.
Black chromium is not glossy and shinyChromium is probably best known from shiny and chrome parts, such rims on cars etc. Therefore, for many perhaps it is hard to imagine black chromium.
Chromium in steel is generally used in order to make it stainless, and is used by the anodization of aluminum, wherein the surface of the work piece is actually being converted to the ruby.
Chrome occurrences worldwideChromium is commercially extracted from the mineral chromites, and the majority of world production comes from South Africa, Kazakhstan, India and Turkey. There are still many untouched deposits of chromites, most are around Kazakhstan and southern Africa.
The pure chromium metal is recovered by heating the chromites along with aluminum and silicon.
The story of chromiumChrome takes its name from the Greek word chroma, meaning color, because they form chemical compounds in many different colors.
In the mid- 1700s, there was discovered an orange- red mineral in the Ural Mountains. Without having total control over what was found, the mineral was called the Siberian red lead. In fact it was lead-chromate, or what we know today as the mineral crocoite.
It was soon common to use minerals as a colorant in paints and textiles, and a yellow color made of crocoite became a trend in the late 1700s.
At the turn of the century to the 1800s found Nicolas- Louis Vauquelin out of mixing crocoite with hydrochloric acid , and by heating the mixture up he got a free metal; chromium. He also found traces of chromium in precious stones like ruby and emerald.
In the 1800s, chrome still primarily used as a dye and leather tanning, but today is used mostly in metal alloys, and a part in the chemical industry.
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