What is Black Iron Oxide and Why Do We Use Them?

25 Aug.,2025

 

Black Iron Oxide uses and applications

Black Iron Oxide

Black iron oxide, also known as magnetite (Fe3O4), is a naturally occurring mineral with a chemical structure consisting of iron (Fe) and oxygen (O). Some key points about black iron oxide:

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  1. Chemical Composition: Black iron oxide has a chemical formula of Fe3O4, indicating that each molecule contains three iron atoms bonded to four oxygen atoms.
  2. Physical Properties: Magnetite typically appears as black or dark brown crystals with a metallic luster.

Black iron oxide is a versatile mineral with diverse applications ranging from pigments and construction materials to environmental remediation and catalysis.

The History of Black Iron Oxide

Black iron oxide, also known as magnetite or ferrous ferric oxide (Fe3O4), has a rich history spanning thousands of years.

  1. Ancient Use: Ancient Egyptians, for instance, used magnetite in their artwork and as a pigment in paints.
  2. Middle Ages: It was used as a pigment in paintings, particularly in creating black paint.
  3. Industrial Revolution: Magnetite was an essential component in the Bessemer process, a revolutionary technique for mass-producing steel.
  4. Modern Applications: Black iron oxide finds applications in a wide range of industries. It is used as a pigment in paints, coatings, and inks due to its black color and resistance to corrosion.

The black iron oxide has played a significant role in various aspects of human civilization, from ancient cultural practices to modern technological advancements. Its versatile properties continue to make it valuable in numerous industries today.

Types of Black Iron Oxide

Black iron oxide, also known as magnetite (Fe3O4), can vary in type and grade depending on factors such as particle size, purity, and intended application.

  1. Pigment-Grade Magnetite: Pigment-grade magnetite is characterized by its deep black color, UV resistance, and chemical stability, making it suitable for applications in paints, coatings, plastics, and inks.
  2. Synthetic Magnetite: Synthetic magnetite can be tailored to exhibit desired properties such as magnetic strength, chemical composition, and surface characteristics.

The choice of black iron oxide depends on factors such as the desired properties, performance requirements, and cost considerations for a particular application or industry.

Also Read: Synthetic Iron Oxide Suppliers and Manufacturers in India

The properties of Black Iron Oxide

Black iron oxide, also known as magnetite (Fe3O4), possesses several unique properties that make it valuable for a variety of applications:

  1. Chemical Composition: Black iron oxide has a chemical formula of Fe3O4, indicating that each molecule contains three iron (Fe) atoms bonded to four oxygen (O) atoms.
  2. Biocompatibility: Magnetite nanoparticles have shown biocompatibility in biomedical applications, making them suitable for use in drug delivery systems, magnetic resonance imaging (MRI) contrast agents, hyperthermia therapy for cancer treatment, and magnetic cell separation techniques.
  3. UV Resistance: Magnetite exhibits excellent UV resistance, making it suitable for outdoor applications where exposure to sunlight may cause color fading or degradation.
  4. Electrical Conductivity: While not as conductive as metals like copper or aluminum, magnetite exhibits some degree of electrical conductivity.

Black iron oxide is crucial for its various industrial and scientific applications, ranging from pigments and magnetic materials to geological studies and electronic devices. Black iron oxide is a versatile material with a wide range of applications across multiple industries, including construction, automotive, electronics, paints and coatings, biomedical, and environmental remediation.

The applications of Black Iron Oxide

The unique properties of Black Iron Oxide contribute to the performance and functionality of a wide range of products. The many applications of black iron oxide versatility, and importance in various industries.

  1. Pigments: Black iron oxide is widely used as a pigment in various industries. Its intense black color makes it valuable for coloring paints, coatings, plastics, inks, and other materials.
  2. Construction Materials: Black iron oxide is added to concrete, asphalt, and other construction materials to improve their density, strength, and resistance to radiation.
  3. Electromagnetic Devices: Black iron oxide is used in the manufacture of electromagnetic devices, such as electromagnetic brakes, clutches, and sensors.

Black iron oxide plays an important role in various industries, emphasizing its versatility and significance in modern-day manufacturing and technological endeavors.

Also Read: Pigment colors for Cosmetics and Personal Care Products

The primary advantages of Black Iron Oxide

Black iron oxide offers several primary advantages across a spectrum of applications. Its properties make it a versatile and valuable material with a wide range of applications across various industries.

  1. Intense Black Color: The intense black hue ensures vibrant and long-lasting coloring in paints, coatings, plastics, inks, and other materials, enhancing their aesthetic appeal.
  2. UV Resistance: The ability to withstand prolonged exposure to sunlight without fading or degrading ensures the longevity and durability of materials colored with magnetite-based pigments.
  3. High Density: Added to concrete to increase its density and improve its strength and radiation shielding properties.

Black iron oxide has a relatively high density compared to other pigments, making it advantageous in applications where density is desired.

Black Iron Oxide Market Analysis

Black iron oxide holds a significant position in the global pigment market. Its versatile properties and wide-ranging applications have propelled its demand across various industries. Iron oxide pigments, derived from iron oxide minerals such as hematite, magnetite, and goethite, offer vibrant colors, excellent durability, and UV stability, making them indispensable in numerous industries.  The Iron Oxide Pigments Market size is estimated at USD 2.43 billion in and is expected to reach USD 3.10 billion by , growing at a CAGR of greater than 4.5% during the forecast period (-).

  1. Construction Industry: The construction sector is a major driver of the black iron oxide market. With increasing urbanization, infrastructure development, and construction activities worldwide, there’s a growing demand for black iron oxide in applications such as concrete coloring, architectural coatings, tiles, and paving stones.
  2. Paints and Coatings: The construction and automotive sectors continue to expand, the demand for black iron oxide in architectural paints, industrial coatings, automotive coatings, and wood coatings is expected to rise.
  3. Plastics Industry: black iron oxide is utilized for coloring various plastic products, including PVC pipes, profiles, sheets, films, and masterbatches.

Black Iron Oxide Market Demand in major regions

The demand for black iron oxide varies across major regions due to differences in industrialization, construction activities, infrastructure development, and manufacturing sectors.

  1. China: The booming construction industry, driven by rapid urbanization and infrastructure development, fuels significant demand for black iron oxide in applications such as concrete coloring, architectural coatings, and construction materials.
  2. India: Expanding manufacturing base, including paints, plastics, and automotive industries, further contributes to the demand for black iron oxide pigments.
  3. United States: The construction industry remains a major consumer of iron oxide pigments, particularly in applications such as colored concrete, paints, coatings, and plastics.
  4. Germany, France, United Kingdom: The demand for iron oxide pigments in architectural coatings, industrial coatings, plastics, and automotive coatings remains significant in these regions.
  5. GCC Countries: The Gulf Cooperation Council (GCC) countries, including Saudi Arabia, UAE, Qatar, and Kuwait, witness substantial demand for black iron oxide due to large-scale infrastructure projects, urban development, and construction activities.

Also Read: UTOX Pigment – Titanium Dioxide Substitute | Paint Chemical | Pigment Colour

Black Iron Oxide Major Suppliers & Traders in India

The several major suppliers and traders of black iron oxide, cater to the diverse needs of industries such as construction, paints and coatings, plastics, and more. Bansal Trading Company is a well-known supplier and trader of black iron oxide in India, offering a comprehensive range of high-quality products tailored to meet various industry requirements. We stand as a prominent supplier and trader of black iron oxide, catering to diverse industrial needs with its quality products and reliable services. We also pride ourselves on sourcing black iron oxide from reputable manufacturers and ensuring product quality and consistency.

Black Iron Oxide at the best price from Manufacturers

Procuring black iron oxide at the best price often involves direct engagement with manufacturers. Bansal Trading Company takes pride in offering high-quality black iron oxide at competitive prices, ensuring value for money for their customers. we are committed to transparency and fairness in pricing, ensuring that customers receive upfront and competitive quotes for their black iron oxide requirements. Their dedicated team works closely with clients to understand their specific needs.

Bansal Trading Company has earned a reputation as a preferred supplier of black iron oxide, trusted by industries across India.

Also Read: Pigment, Iron Oxide and Titanium Dioxide Manufacturers and Suppliers

Conclusion

Iron(II,III) oxide - Wikipedia

Iron(II,III) oxide Names IUPAC name iron(II) diiron(III) oxide[1] Other names ferrous ferric oxide, ferrosoferric oxide, iron(II,III) oxide, magnetite, black iron oxide, lodestone, rust Identifiers
  • -61-9 Y
3D model (JSmol) ChEBI
  • CHEBI: Y
ChEMBL
  • ChEMBL N
ChemSpider
  •  Y
ECHA InfoCard 100.013.889 PubChem CID UNII
  • XM0M87F357 Y
CompTox Dashboard (EPA)
  • InChI=1S/3Fe.4O YKey: SZVJSHCCFOBDDC-UHFFFAOYSA-N Y
  • InChI=1/3Fe.4O/rFe3O4/c1-4-2-6-3(5-1)7-2Key: SZVJSHCCFOBDDC-QXRQKJBKAR
  • O1[Fe]2O[Fe]O[Fe]1O2
Properties Fe3O4

FeO.Fe2O3

Molar mass 231.533 g/mol Appearance solid black powder Density 5 g/cm3 Melting point 1,597 °C (2,907 °F; 1,870 K) Boiling point 2,623[2] °C (4,753 °F; 2,896 K) Refractive index (nD) 2.42[3] Hazards NFPA 704 (fire diamond) Thermochemistry Std enthalpy of
formation (ΔfH⦵298) −.89 kJ·mol−1[4] Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N   (what is YN ?) Chemical compound

Iron(II,III) oxide, or black iron oxide, is the chemical compound with formula Fe3O4. It occurs in nature as the mineral magnetite. It is one of a number of iron oxides, the others being iron(II) oxide (FeO), which is rare, and iron(III) oxide (Fe2O3) which also occurs naturally as the mineral hematite. It contains both Fe2+ and Fe3+ ions and is sometimes formulated as FeO ∙ Fe2O3. This iron oxide is encountered in the laboratory as a black powder. It exhibits permanent magnetism and is ferrimagnetic, but is sometimes incorrectly described as ferromagnetic.[5] Its most extensive use is as a black pigment (see: Mars Black). For this purpose, it is synthesized rather than being extracted from the naturally occurring mineral as the particle size and shape can be varied by the method of production.[6]

Preparation

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Heated iron metal interacts with steam to form iron oxide and hydrogen gas.

3 Fe + 4 H 2 O ⟶ Fe 3 O 4 + 4 H 2 {\displaystyle {\ce {3Fe + 4H2O->Fe3O4 + 4H2}}}

Under anaerobic conditions, ferrous hydroxide (Fe(OH)2) can be oxidized by water to form magnetite and molecular hydrogen. This process is described by the Schikorr reaction:

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3 Fe ( OH ) 2 ferrous hydroxide ⟶ Fe 3 O 4 magnetite + H 2 hydrogen + 2 H 2 O water {\displaystyle {\ce {{\underset {ferrous\ hydroxide}{3Fe(OH)2}}->{\underset {magnetite}{Fe3O4}}+{\underset {hydrogen}{H2}}+{\underset {water}{2H2O}}}}}

This works because crystalline magnetite (Fe3O4) is thermodynamically more stable than amorphous ferrous hydroxide (Fe(OH)2 ).[7]

The Massart method of preparation of magnetite as a ferrofluid, is convenient in the laboratory: mix iron(II) chloride and iron(III) chloride in the presence of sodium hydroxide.[8]

A more efficient method of preparing magnetite without troublesome residues of sodium, is to use ammonia to promote chemical co-precipitation from the iron chlorides: first mix solutions of 0.1 M FeCl3·6H2O and FeCl2·4H2O with vigorous stirring at about rpm. The molar ratio of the FeCl3:FeCl2 should be about 2:1. Heat the mix to 70 °C, then raise the speed of stirring to about rpm and quickly add a solution of NH4OH (10 volume %). A dark precipitate of nanoparticles of magnetite forms immediately.[9]

In both methods, the precipitation reaction relies on rapid transformation of acidic iron ions into the spinel iron oxide structure at pH 10 or higher.

Controlling the formation of magnetite nanoparticles presents challenges: the reactions and phase transformations necessary for the creation of the magnetite spinel structure are complex.[10] The subject is of practical importance because magnetite particles are of interest in bioscience applications such as magnetic resonance imaging (MRI), in which iron oxide magnetite nanoparticles potentially present a non-toxic alternative to the gadolinium-based contrast agents currently in use. However, difficulties in controlling the formation of the particles, still frustrate the preparation of superparamagnetic magnetite particles, that is to say: magnetite nanoparticles with a coercivity of 0 A/m, meaning that they completely lose their permanent magnetisation in the absence of an external magnetic field. The smallest values currently reported for nanosized magnetite particles is Hc = 8.5 A m−1,[11] whereas the largest reported magnetization value is 87 Am2 kg−1 for synthetic magnetite.[12][13]

Pigment quality Fe3O4, so called synthetic magnetite, can be prepared using processes that use industrial wastes, scrap iron or solutions containing iron salts (e.g. those produced as by-products in industrial processes such as the acid vat treatment (pickling) of steel):

  • Oxidation of Fe metal in the Laux process where nitrobenzene is treated with iron metal using FeCl2 as a catalyst to produce aniline:[6]
C6H5NO2 + 3 Fe + 2 H2O → C6H5NH2 + Fe3O4
  • Oxidation of FeII compounds, e.g. the precipitation of iron(II) salts as hydroxides followed by oxidation by aeration where careful control of the pH determines the oxide produced.[6]

Reduction of Fe2O3 with hydrogen:[14][15]

3Fe2O3 + H2 → 2Fe3O4 +H2O

Reduction of Fe2O3 with CO:[16]

3Fe2O3 + CO → 2Fe3O4 + CO2

Production of nano-particles can be performed chemically by taking for example mixtures of FeII and FeIII salts and mixing them with alkali to precipitate colloidal Fe3O4. The reaction conditions are critical to the process and determine the particle size.[17]

Iron(II) carbonate can also be thermally decomposed into Iron(II,III):[18]

3FeCO3 → Fe3O4 + 2CO2 + CO

Reactions

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Reduction of magnetite ore by CO in a blast furnace is used to produce iron as part of steel production process:[5]

Fe 3 O 4 + 4 CO ⟶ 3 Fe + 4 CO 2 {\displaystyle {\ce {{Fe3O4}+ 4CO -> {3Fe}+ 4CO2}}}

Controlled oxidation of Fe3O4 is used to produce brown pigment quality γ-Fe2O3 (maghemite):[19]

2 Fe 3 O 4 ⏟ magnetite + 1 2 O 2 ⟶ 3 ( γ − Fe 2 O 3 ) ⏟ maghemite {\displaystyle {\ce {\underbrace{2Fe3O4}_{magnetite}+ {1/2O2}->}}\ {\color {Brown}{\ce {\underbrace{3(\gamma-Fe2O3)}_{maghemite}}}}}

More vigorous calcining (roasting in air) gives red pigment quality α-Fe2O3 (hematite):[19]

2 Fe 3 O 4 ⏟ magnetite + 1 2 O 2 ⟶ 3 ( α − Fe 2 O 3 ) ⏟ hematite {\displaystyle {\ce {\underbrace{2Fe3O4}_{magnetite}+ {1/2O2}->}}\ {\color {BrickRed}{\ce {\underbrace{3(\alpha-Fe2O3)}_{hematite}}}}}

Structure

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Fe3O4 has a cubic inverse spinel group structure which consists of a cubic close packed array of oxide ions where all of the Fe2+ ions occupy half of the octahedral sites and the Fe3+ are split evenly across the remaining octahedral sites and the tetrahedral sites.

Both FeO and γ-Fe2O3 have a similar cubic close packed array of oxide ions and this accounts for the ready interchangeability between the three compounds on oxidation and reduction as these reactions entail a relatively small change to the overall structure.[5] Fe3O4 samples can be non-stoichiometric.[5]

The ferrimagnetism of Fe3O4 arises because the electron spins of the FeII and FeIII ions in the octahedral sites are coupled and the spins of the FeIII ions in the tetrahedral sites are coupled but anti-parallel to the former. The net effect is that the magnetic contributions of both sets are not balanced and there is a permanent magnetism.[5]

In the molten state, experimentally constrained models show that the iron ions are coordinated to 5 oxygen ions on average.[20] There is a distribution of coordination sites in the liquid state, with the majority of both FeII and FeIII being 5-coordinated to oxygen and minority populations of both 4- and 6-fold coordinated iron.

Properties

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Fe3O4 is ferrimagnetic with a Curie temperature of 858 K (585 °C). There is a phase transition at 120 K (−153 °C), called Verwey transition where there is a discontinuity in the structure, conductivity and magnetic properties.[21] This effect has been extensively investigated and whilst various explanations have been proposed, it does not appear to be fully understood.[22]

While it has much higher electrical resistivity than iron metal (96.1 nΩ m), Fe3O4's electrical resistivity (0.3 mΩ m [23]) is significantly lower than that of Fe2O3 (approx kΩ m). This is ascribed to electron exchange between the FeII and FeIII centres in Fe3O4.[5]

Uses

[edit] Pharmaceutical compound FerumoxytolClinical dataTrade namesFeraheme, RiensoAHFS/Drugs.comMonographMedlinePlusaLicense dataRoutes of
administrationIntravenous infusionATC code
  • None
Legal statusLegal statusIdentifiers
  • iron(2+);iron(3+);oxygen(2-)
CAS Number
  • -38-2 Y
DrugBankUNIIKEGGChEBICompTox Dashboard (EPA)ECHA InfoCard100.013.889 Chemical and physical dataFormulaFe3O4Molar mass 231.531 g·mol−13D model (JSmol)
  • [O-2].[O-2].[O-2].[O-2].[Fe+2].[Fe+3].[Fe+3]
  • InChI=1S/3Fe.4O/q+2;2*+3;4*-2
  • Key:WTFXARWRTYJXII-UHFFFAOYSA-N

Fe3O4 is used as a black pigment and is known as C.I pigment black 11 (C.I. No.) or Mars Black.[19]

Fe3O4 is used as a catalyst in the Haber process and in the water-gas shift reaction.[27] The latter uses an HTS (high temperature shift catalyst) of iron oxide stabilised by chromium oxide.[27] This iron–chrome catalyst is reduced at reactor start up to generate Fe3O4 from α-Fe2O3 and Cr2O3 to CrO3.[27]

Bluing is a passivation process that produces a layer of Fe3O4 on the surface of steel to protect it from rust. Along with sulfur and aluminium, it is an ingredient in steel-cutting thermite.[citation needed]

Medical uses

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Nano particles of Fe3O4 are used as contrast agents in MRI scanning.[28]

Ferumoxytol, sold under the brand names Feraheme and Rienso, is an intravenous Fe3O4 preparation for treatment of anemia resulting from chronic kidney disease.[24][25][29][30] Ferumoxytol is manufactured and globally distributed by AMAG Pharmaceuticals.[24][30]

Biological occurrence

[edit]

Magnetite has been found as nano-crystals in magnetotactic bacteria (42–45 nm)[6] and in the beak tissue of homing pigeons.[31]

References

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