Chromium is an inactive metal and is stable to oxygen and moisture at room temperature, but it reacts with fluorine to form CrF3. When the temperature is higher than 600 degree , chromium reacts with water, nitrogen, carbon and sulfur to form the corresponding Cr2O3, Cr2N and CrN, Cr7C3 and Cr3C2, C r2S3.
The reaction between chromium and oxygen starts quickly, and the speed slows down sharply when an oxide film is formed on the surface. When heated to 1200 degree , the oxide film is destroyed and the oxidation speed accelerates again. At 2000 degree , chromium burns in oxygen to generate Cr2O3. Chromium reacts easily with dilute hydrochloric acid or dilute sulfuric acid to form chloride or sulfate, while releasing hydrogen.
Due to the brittleness of chromium alloys, chromium is mainly used in the production of stainless steel and various alloy steels in the form of iron alloys (such as ferrochromium). Metal chromium is used as an additive for aluminum alloys, cobalt alloys, titanium alloys, high-temperature alloys, resistance heating alloys, etc. Chromium oxide is used as a light-resistant and heat-resistant coating, an abrasive, a colorant for glass and ceramics, and a catalyst for chemical synthesis.
Chromium vitriol and dichromate are used as tanning materials for leather, mordant, impregnating agent and various pigments for fabric dyeing. Chrome plating and chromium infiltration can make steel, copper, aluminum and other metals form a corrosion-resistant surface layer that is bright and beautiful. It is widely used in industries such as furniture, automobiles, and construction. In addition, chromium ore is also widely used in the production of refractory materials.
In the metallurgical industry, chromite is mainly used to produce ferrochrome alloys and metallic chromium. Chromium ferroalloy is used as an additive to steel to produce a variety of special steels with high strength, corrosion resistance, wear resistance, high temperature resistance, and oxidation resistance, such as stainless steel, acid-resistant steel, heat-resistant steel, ball bearing steel, spring steel, tool steel, etc.
