Iron oxide pigments, which can be natural or synthetic, have been used as colorants since early man began painting on cave walls. Natural pigments come from several iron oxide minerals: red pigments come from hematite. Yellow and brown pigments -- ochre, mountain ranges and sepia -- come from limonite. Magnetite provides black iron oxide pigments. Mica iron oxide is a special form of hematite present in thin metallic gray flakes or flakes. Synthetic pigments are manufactured under controlled conditions so that particle size, distribution and shape can be accurately replicated, resulting in superior uniformity, color quality and chemical purity.
Iron oxide pigments are relatively low cost materials that resist color change due to exposure to sunlight, have good chemical resistance, and are stable under normal environmental conditions.
Mica iron oxides give paints and coatings unique properties because of the flake particle arrangement that resists the penetration of moisture and gases. These coatings prevent corrosion and rusting of metals, and also prevent blistering, cracking and flaking.
Iron oxide pigments are produced by steelmaking. When steel is treated with hydrochloric acid to remove surface oxides, the acid is regenerated for recycling and produces iron oxide. Regenerated iron oxide is used in a variety of filters, inductors and transformers in household appliances and industrial equipment, as well as flexible magnets, generators, loudspeakers and electric vehicle motors.
The primary applications for iron oxide pigments are paints, coatings and building materials such as concrete products, mortars, paving stones and roofing tiles. Natural pigments are used in primers and basecoats where color consistency is less important, while synthetic pigments are used in topcoat coatings where color consistency is important.
New developments in the synthetic iron oxide pigment industry in recent years include iron oxide in particulate form and new versions of nanomaterials that are being used in computer disk drives and high-performance speakers, as well as in biology and medicine, including magnetic resonance imaging.
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