Chemical Properties of Iron Oxide Red
Formula: Fe2O3
Molecular Weight: 159.69
CAS No.: 1332-37-2

Iron Oxide Red, also known as ferric oxide red, iron red, or rust red, is a trigonal crystal system powder ranging from orange-red to purplish-red. It exists in both natural and synthetic forms.

The natural form of iron oxide red is called sienna, with a relative density of 55.25. Its fineness ranges from 0.4 to 20 μm. It decomposes at a melting point of 1565°C. When calcined, it releases oxygen and can be reduced to iron by hydrogen and carbon monoxide. It is insoluble in water, soluble in hydrochloric acid and sulfuric acid, and slightly soluble in nitric acid and alcohols. Natural iron oxide red exhibits excellent light resistance, high-temperature resistance, acid resistance, alkali resistance, and rust prevention. It has good dispersibility, strong tinting strength, and hiding power, with no oil or water bleeding. It is non-toxic. The maximum allowable concentration in the air is 5 mg/m3.

Specialized Uses of Iron Oxide Red

Iron oxide red is widely used in industries such as construction, rubber, plastics, and coatings. Particularly, iron red primer offers rust prevention functionality and can replace expensive red lead paint, thereby saving non-ferrous metals.
Iron oxide red is also a high-precision grinding material used for polishing precision hardware instruments and optical glass. High-purity iron oxide red serves as the main base material for powder metallurgy, used in smelting various magnetic alloys and other high-grade alloy steels. It is produced by high-temperature calcination of ferrous sulfate, yellow iron oxide, or scrap iron, or directly synthesized from liquid media.