The abundance of chromium in the earth's crust is 0.018%. The most important minerals chromium chromium iron ore (FeCr 2 O 4 or FeO.Cr2O3). The chromite is iron black or brownish black, similar to magnetite, but its magnetic properties are very weak, generally in the form of blocks, dots, beans, strips, and the like. This kind of mine is particularly bright when viewed in the sun. Sometimes it has yellow spots on the surface. The knife can be infused and is often produced in green igneous rocks (olivine, serpentine). Other Accessories,Popular Shower Door Handle,Stainless Steel Dust Proof,Black Glass Door Knobs ONLEE HARDWARE CO.,LTD , https://www.onleehardware.com
The chrome compounds are colourful and colorful. Bai Xueliang silver metallic chromium and chromium sulfate are green, yellow chromium magnesium, potassium dichromate is orange, scarlet is chromic acid, chromium oxide green, chrome alum blue violet , lead chromate is yellow...
The melting point of chromite is as high as 1900 °C - 2050 °C, it can keep the volume at high temperature, and it does not react with any slag. Therefore, it can be used as a refractory material, a steelmaking furnace and a lining of a non-ferrous metal smelting furnace.
Of all the metals, chromium is the hardest one. Chromium is often incorporated into steel to make a hard, corrosion-resistant alloy. Most of the world's chromium is used to make a variety of alloys. Chromium steel is a good material for manufacturing machinery, gun barrels, tanks and armored vehicles. In nature, chromium is often present in the chromite ore together with iron, and is directly smelted with chromite. The steel that is produced is chrome steel.
When steel is added, 12% or more of chromium, or 18% of chromium and 8% of nickel are added , and the steel obtained is stainless steel. When stainless steel encounters corrosive substances, it forms a fine and solid chrome oxide film on its surface, protecting the internal metal from corrosion. Some stainless steel can maintain it even at 800 °C. Its excellent performance.
In 1974, Qin Shihuang’s burial pottery pit was discovered in Linyi, Shaanxi Province. Three swords were unearthed, and the sword was black and bright. These swords were buried in the wet soil of five or six meters deep for more than two thousand years. When they were unearthed, they were not only rustless, but also sharp enough to cut through a dozen newspapers at once. After testing and analysis by relevant experts, the surface treatment of the three swords was based on the chromium salt oxidation method. Chromate is a very strong oxidant that creates a dense and stable oxide film on the surface metal of the sword, thus protecting the internal metal. It should be noted that this chromium salt passivation treatment technology was not applied to metal corrosion in foreign countries until the 1930s.
Metallic chromium is mainly used for electroplating. When chrome is applied, the thinner the chrome layer, the closer it is to the surface of the metal. Some barrels, the inner wall of the barrel, are plated with a chrome layer that is only five thousandths of a millimeter thick, but after firing thousands of rounds of ammunition and bullets, the chrome layer still exists.
Potassium dichromate is an important chromium compound. In the tanning industry, potassium dichromate is often used in place of tantalum tantalum. In chemical laboratories, it is often dissolved in concentrated sulfuric acid or concentrated nitric acid to form a "washing liquid" that can wash away oil stains and stains on glass instruments. Analytically, potassium dichromate is often used as an oxidant to determine the iron content of iron ore. This method is called "potassium dichromate method". 