Our history of generating chromium oxide green dates back to 1994.
Most of our products use the process of reducing chromium anhydride (CrO3) to chromium oxide green at high temperature. Although this process is more expensive than other processes (such as sodium dichromate-sulfur), we pay more attention to the quality advantage of products compared with the cost.
We have been promoting the prevention and control of “hexavalent chromium”. Hexavalent chromium not only affects the environmental protection standards of products, but also increases the exposure risk of users. We continue Jirong® “Zero Hexavalent Chromium” process to ensure that our products meet more local laws and regulations and environmental restrictions.
We have always believed that quality is the first competitiveness, and we ensure that our products are consistent by scientific production and management. Our commitment to customer satisfaction is conveyed by quality policy. We have been implementing the quality management system (ISO 9001) and environmental management system (ISO 14001) of the International Standardization Organization (ISO), and strictly abide by the system standards to constrain ourselves.
Chromium is a common chemical element found in nature. It has the 21st largest mass fraction in the earth’s crust at 0.0100%. Chromium is often found in nature in the form of chromite. Chromium belongs to the transition metal elements can also be called chromium sub-group elements (i.e., chromium, molybdenum, tungsten), but also transition metals in the latest discovery of one.
Chromium has the symbol Cr, atomic number 24, atomic weight 51.9961 u, and is the first element in group VI. Chromium is a silvery-gray, metallic, hard and brittle transition metal with a Mohs hardness of 8.5, the highest of any metal. Chromium is a highly valued metal that is highly polished and resistant to rust; it is also a major additive to stainless steel, providing it with corrosion protection properties. Polished chromium reflects about 70% of visible light and almost 90% of infrared light.
In 1761, the German Johann Gottlob Lehmann discovered a reddish-orange metallic ore in the Ula Mountains, named Siberian red lead, but this ore actually consisted of chrome-lead ore.In 1770, Peter Simon Pallas was at the same location and saw this ore. This metal was brought back to Europe and used as a pigment, in oil paintings and other places. At that time, all European chrome-lead ores had to be imported from Russia, and the production was small.In 1797, the Frenchman Louis-Nicolas Vauclain was given some samples of chrome-lead ore. He reduced it with carbon and made chromium metal. He boiled Siberian red lead ore with potassium carbonate to obtain the expected precipitate of lead carbonate and a bright yellow solution of unknown nature. To this yellow solution he added a solution of high mercury salts, and a beautiful red solution appeared; to a solution of lead salts, a brilliant yellow precipitate; and to a solution of stannous chloride, the solution changed to a crisp green. Because chromium can generate beautiful multicolored compounds, such as chromium metal is silver-white and snowy, chromium sulfate is green, magnesium chromate is yellow, potassium dichromate is orange-red, chromic acid is scarlet, chromium oxide is green, chromium alum is blue-violet, and lead chromate is yellow, so it will be named according to the Greek word chroma (color), chromium is the American English with the Latin word, according to the chromium is an American and Latin word based on the word chrome, plus the endings -ium commonly used for metal ions. In French and British English Chrome, and in German Chromium, is pronounced [gè] in modern Standard Chinese.
Although chromium was officially discovered in Europe in 1797, it was used early in Chinese history, with the outer layers of a number of Qin Dynasty bronze swords excavated from pit 2 of the Terracotta Warriors in Xi’an plated with chromium. Metals with chromium increase corrosion resistance, such as stainless steel with chromium, which prevents rusting.
Because chromium has many single electrons and strong metallic bonds, chromium has a high hardness and melting point. Chromium is the hardest transition metal. And because of the good mechanical strength of chromium, its corrosion resistance is excellent, so it is often used in alloy steel, semiconductors, coatings and some special environments. In addition, chromium increases the luster of metal surfaces, such as bicycles and automobiles flash metal surfaces may be plated with chromium.
Chromium oxide green: also known as chromium trioxide, chemical formula Cr2O3, is a green crystalline powder, insoluble in water, acid and alkali solutions, soluble in hot alkali metal bromate solutions. Most industrial chromium oxide green is obtained by calcination with chromic anhydride/sodium dichromate.
Sodium dichromate: also known as sodium red alum, chemical formula for Na2Cr2O7, for the orange-red monoclinic prismatic cone or fine needle-like crystals. Easily soluble in water, its aqueous solution is acidic, insoluble in alcohol. Easily deliquescent, pulverized. Strong oxidizing agent. Dangerous goods of class 6.1(a).
Chromic anhydride: also known as chromium trioxide, is an inorganic compound, the chemical formula is CrO3, for the dark reddish purple crystalline powder or flakes, soluble in water, sulfuric acid, nitric acid, ethanol, ether, acetic acid, acetone. It is class 5.1 dangerous goods. The production process of chromic anhydride mainly includes sulfuric acid method and electrolysis method, which is obtained by acidification or electrolysis with sodium dichromate.
Chromium hydroxide: chemical formula is Cr(OH)3, it is gray-green powder, when precipitated in aqueous solution, it is in the form of colloid. Insoluble in water, soluble in acid when first precipitated, but insoluble when left for a long time. It is soluble in caustic alkali and becomes chromite, so it has the same two properties as aluminum hydroxide. Chromium hydroxide can be manufactured in a number of ways, but most chromium hydroxide is obtained from aqueous solutions of sodium chromate.
The most stable green pigment known
Chromium oxide green, also known as chromium trioxide, molecular formula Cr2O3, relative molecular weight 151.99, green crystalline powder, hexagonal crystal system. Density 5.21g/cm3, Mohs hardness 8.5~9 (close to corundum and silicon carbide, second only to diamond), refractive index 2.5 (good hiding power), specific heat capacity (20℃)/0.17J/(g-K). Insoluble in water, acid and organic solvents, slightly soluble in concentrated sodium hydroxide solution, hot concentrated perchloric acid solution and boiling sulfur phosphorus mixed acid. Stable to heat, melting point 2265℃, boiling point about 3000℃, is a high-quality refractory material. It is extremely stable to light, atmosphere and corrosive gases (H2S, SO2, etc.) and has excellent weather resistance.
Chromium oxide green at high temperature can be reduced to chromium metal by hydrogen, alkali metals and alkaline earth metals, silicon, aluminum, carbon, hydrocarbons. Heated with hydrogen chlorine to produce chromium chloride. When heated with soda ash, it produces sodium chromite, and when stored in air, it produces sodium chromate.
The main applications of chromium oxide green are metallurgy, pigment, abrasive, refractory and meltblown coating. Chrome oxide green for metallurgy (aluminum thermal method of preparing chromium metal) accounts for the largest proportion of production. Secondly, it is used as a green pigment in paints, coatings, ceramics, enamels, colored cements, plastics and so on. Chromium oxide green can reflect infrared rays similar to chlorophyll, and is often used to prepare camouflage coatings similar to clusters of green leaves, and chromium oxide green is often referred to as the green of recent nature. As an abrasive, it is used for grinding and polishing of machinery, meters, instruments, clocks and ball bearings. Directly as refractory material, or with magnesium oxide, alumina, zirconium oxide, etc. to make refractory products or unqualified refractory materials. As a meltblown coating with the help of plasma sprayed directly onto the surface of metals and ceramics, giving the latter a very high hardness and abrasion resistance, corrosion resistance and high temperature resistance. In addition, chromium oxide green can also be used as a catalyst or its carrier for the production of compliant oxides, as well as raw materials for the preparation of chromium carbides, nitrides, borides, silicides.
Crystal structure： Cr2O3 has same crystal structure as α-Al2O3 , which is trigonal system (R-3C)，if a hexagonal cell is taken, the lattice parameter is about a=b=4.9588Å，c=13.5942Å (JCPDS card no.38-1479). Such crystal structure is constitute by the octahedral void formed by O2-Ion dense pile and Cr3+ion fill. Given that the Cr3+ is located in the octahedral space with radius of Cr3+ and O2-ion, which is respectively 0.069nm and 0.132nm, the radius ratio of positive and negative ions is 0.520 (within the range of 0.414-0.732), and the coordination number is 6, that is, one Cr3+ ion is surrounded by six O2-ions.
As the main green pigment used, it complies with most regulations and restrictions
Its unique physical and chemical properties have led to more applications in high-temperature materials, friction materials, and electrochemistry.
Basic raw materials for producing metallic chromium