Iron oxide pigments are a significant class of inorganic colorants with the basic component being iron oxides. They rank as the second – largest inorganic pigments after titanium dioxide and the foremost colored inorganic pigments, finding extensive use in both industrial and daily – life applications.
Chemically, they mainly include four categories: iron oxide red, iron oxide yellow, iron oxide black, and iron oxide brown. Among them, iron oxide red is the most common, accounting for about 50% of the total iron oxide pigments. Additionally, micaceous iron oxide, used as an anti – rust pigment, and magnetic iron oxide, for magnetic recording materials, also fall within the scope of iron oxide pigments. Different types of iron oxide pigments present a rich spectrum of colors due to varying oxidation states of iron. For example, iron oxide red, derived from ferric oxide (Fe₂O₃), appears red; iron oxide yellow, from hydrated ferric oxide (Fe₂O₃·H₂O), is yellow; and iron oxide black, which is magnetite (Fe₃O₄), shows black.
In terms of performance, iron oxide pigments are remarkable. Their acid and alkali resistance is excellent. They are highly stable against various concentrations of alkalis and commonly used building materials like cement and lime mortar, without causing powdering of cement building components or affecting their strength. However, they gradually dissolve in strong acids, especially under heating and high – concentration conditions. Regarding light and heat resistance, ordinary iron oxide pigments are stable within a certain temperature range. For instance, iron oxide yellow turns red – hued when exceeding 130°C, and iron oxide red deepens to dark red above 300°C. Nevertheless, many enterprises have now developed products with superior performance that can withstand higher temperatures. Their weather resistance is outstanding, with little impact from climatic conditions such as cold, heat, dryness, and humidity in the atmosphere, making them prominent in outdoor applications. Moreover, they are stable in polluted gases, insoluble in water, mineral oils, vegetable oils, and many organic solvents, and show no penetration.
Post time:
May-07-2025
