Product Description
Iron Oxide Red is an inorganic pigment primarily composed of iron(III) oxide, with the chemical formula Fe2O3 and CAS number 1309-37-1. It is commonly identified as C.I. Pigment Red 101 and is widely used where durable red coloration and earth-tone shades are required.
Unlike soluble colorants, Iron Oxide Red functions as a particulate pigment dispersed throughout a host material. Its performance is therefore influenced by particle characteristics, dispersion quality, pigment concentration, and compatibility with the binder or substrate. The resulting shade may range from a warm red to a deeper or more brownish red, depending on the pigment grade and the materials used.
Typical application areas include construction materials, paints and coatings, plastics, rubber products, ceramics, and selected paper or surface-finishing systems. In cementitious products, pigment dispersion and dosage affect the final appearance; in coatings and polymers, particle distribution and processing conditions influence color uniformity and finish.
Commercial grades may differ in purity, manufacturing method, particle size, undertone, tinting strength, moisture content, and other technical parameters. For this reason, the product should be selected against an application-specific specification rather than by color name alone. Buyers should review the current Certificate of Analysis (COA) and technical data before confirming suitability for a particular process.
Chemical Properties
| Property | Details |
|---|---|
| Product Name | Iron Oxide Red |
| CAS Number | 1309-37-1 |
| Chemical Name | Iron(III) oxide |
| Common Synonyms | Red Iron Oxide; Ferric Oxide; Ferric Oxide Red; Diiron Trioxide |
| Color Index Name | C.I. Pigment Red 101 |
| Color Index Number | C.I. 77491 |
| Molecular Formula | Fe2O3 |
| Molecular Weight | Approximately 159.69 g/mol |
| Chemical Class | Inorganic iron oxide pigment |
| Appearance | Typically red to reddish-brown powder; shade depends on grade |
| Water Solubility | Insoluble in water |
| Density | Approximately 5.2 g/cm³ for iron(III) oxide; verify the measured value for the supplied pigment grade |
| Thermal Behavior | High thermal stability for the anhydrous oxide; performance in a formulation depends on processing conditions |
| Key Grade Parameters | Fe2O3 content, shade, tinting strength, particle fineness, moisture, pH, oil absorption |
| Storage | Keep the container closed and store in a dry area, following the supplied safety documentation |
Product Applications
1. Construction Materials
Iron Oxide Red is used to color cement-based products such as concrete blocks, paving units, mortar, and other architectural materials. The pigment should be dispersed uniformly, and dosage should be established through trials because cement type, aggregate color, water content, and curing conditions can affect the finished shade.
2. Paints and Industrial Coatings
The pigment can be incorporated into compatible coating systems to produce red or earth-tone finishes. Formulators should evaluate tinting strength, dispersion, binder compatibility, film appearance, and exposure requirements before selecting a grade.
3. Plastics and Rubber
Iron Oxide Red may be used to color selected plastic and rubber compounds. Grade selection should account for processing temperature, polymer compatibility, dispersion equipment, and the target color.
4. Ceramic and Building Products
It can be considered for coloring suitable ceramic bodies, tiles, and other mineral-based products. Testing under the intended firing or processing conditions is necessary to confirm shade development and compatibility.
5. Paper and Surface-Finishing Applications
Selected grades may be used in compatible paper-coloring, polishing, or surface-finishing processes. The required particle size, purity, and surface characteristics should be checked for the intended use.
6. Color Matching and Formulation Development
Iron Oxide Red can be used to adjust red and earth-tone shades in pigment blends. Laboratory trials help determine the required addition level and evaluate interactions with other formulation components.
FAQ
Q1: What is Iron Oxide Red?
Iron Oxide Red is an inorganic pigment primarily composed of iron(III) oxide, Fe2O3. It is used to impart red and reddish-brown shades to compatible materials.
Q2: What is the CAS number of Iron Oxide Red?
The CAS number is 1309-37-1. The material is commonly associated with C.I. Pigment Red 101 and C.I. 77491.
Q3: Is Iron Oxide Red soluble in water?
No. Iron(III) oxide is insoluble in water. In practical formulations, the pigment is distributed by dispersion rather than dissolved.
Q4: Which industries use Iron Oxide Red?
Common application areas include construction materials, paints and coatings, plastics, rubber, ceramics, and selected paper or surface-finishing processes. The appropriate grade depends on the technical requirements of each application.
Q5: Which specifications should be checked before purchase?
Review iron oxide content, shade, tinting strength, particle fineness, moisture, pH, oil absorption, and any application-specific performance data. Confirm the acceptance limits with the current product specification and COA.
Q6: Is every Iron Oxide Red grade suitable for outdoor use?
Not automatically. Iron oxide pigments are generally known for good light and weather resistance, but performance depends on pigment quality, formulation, substrate, and exposure conditions. Validate the selected grade in the intended end-use system.
