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CAS Number: 51274-00-1
EC Number: 215-168-2
C.I. Number: 77492
Molecular Formula: Fe₂O₃·H₂O (FeOOH)
Molecular Weight: 159.69 g/mol (as Fe₂O₃)
Synonyms:
C.I. Pigment Yellow 42; Pigment Yellow 42; Iron(III) oxide-hydroxide; Ferric oxide monohydrate; Hydrated ferric oxide; Yellow ferric oxide; Iron oxide yellow monohydrate; Goethite; Yellow iron oxide pigment; Transparent iron oxide yellow; Synthetic yellow iron oxide
Chemical Identity and Properties:
Yellow iron oxide is an inorganic pigment composed of hydrated iron(III) oxide. The compound exists naturally as the mineral goethite but is predominantly manufactured synthetically for commercial applications. The pigment consists of needle-shaped (acicular) crystals that give it excellent tinting strength and dispersibility. The color ranges from lemon yellow to reddish-yellow depending on particle size, shape, and the degree of hydration.
Physical Properties:
Appearance: Yellow to reddish-yellow powder
Density: 5.24 g/cm³
Bulk Density: 0.5–1.0 g/cm³
Hardness (Mohs): 5–5.5
pH (10% slurry): 3.0–7.0
Oil Absorption: 25–35 g/100 g
Particle Size: 0.1–0.5 µm (opaque grades); 0.05–0.1 µm (transparent grades)
Specific Surface Area: 5–20 m²/g (opaque); 30–80 m²/g (transparent)
Melting Point: Decomposes at 1538 °C
Refractive Index: 2.2–2.4 (high hiding power)
Pigment Properties:
Color Index: PY42
Lightfastness: 8 (excellent) on a scale of 1–8
Weather Resistance: Excellent for exterior applications
Heat Stability: Up to 300 °C for transparent grades; up to 800 °C for opaque grades
Chemical Resistance: Resistant to weak acids, alkalis, organic solvents, and water
Dispersibility: Good to excellent depending on surface treatment
Manufacturing Process:
Synthetic Production:
Yellow iron oxide is manufactured through controlled chemical precipitation:
Method 1: Precipitation and Oxidation
Iron(II) sulfate (FeSO₄·7H₂O) is dissolved in water
Neutralized with sodium hydroxide or calcium hydroxide to form iron(II) hydroxide
Aerated under controlled conditions to oxidize iron(II) to iron(III), forming goethite crystals
Filtered, washed, dried, and milled
Method 2: Penniman Process
Uses iron metal scrap, iron(II) sulfate, and an oxidizing agent
Produces acicular particles with superior pigmentary properties
Allows control over particle size and shape to achieve specific color characteristics
Method 3: Thermal Decomposition
Calcination of iron(II) salts under controlled conditions
Produces pigments with specific crystal structures
Applications:
1. Paints and Coatings:
Yellow iron oxide is widely used in:
Decorative paints: Interior and exterior wall paints, trim paints
Industrial coatings: Primers, anti-corrosive coatings, machinery enamels
Automotive coatings: Primers, undercoats, specialty finishes
Marine coatings: Anticorrosive primers, deck paints
Powder coatings: Architectural and industrial finishes
Wood stains: Transparent yellow iron oxide for wood finishes
2. Construction and Building Materials:
Concrete products: Colored concrete blocks, pavers, tiles, and precast elements
Cement: Integral colored cement for floors, walls, and architectural features
Mortar and stucco: Colored mortars, plasters, and renders
Roofing: Colored roof tiles and shingles
Asphalt: Decorative colored asphalt for pathways and recreational areas
Landscaping: Colored aggregates and decorative concrete
3. Plastics and Polymers:
Polyvinyl chloride (PVC): Window profiles, pipes, flooring, and siding
Polyolefins: Polyethylene and polypropylene for outdoor applications
Engineering plastics: ABS, nylon, polycarbonate for automotive and consumer goods
Rubber: Tires, hoses, gaskets, and molded goods
Masterbatches: Color concentrates for all plastic types
4. Cosmetics:
Yellow iron oxide is a standard pigment in cosmetic formulations:
Foundations: Liquid, cream, powder, and stick foundations
Face powders: Loose and pressed powders
Concealers: Cream and liquid concealers
Blushes and bronzers: Powder and cream formulations
Eye makeup: Eyeshadows, eyeliners, eyebrow pencils
Lip products: Lipsticks, lip glosses, lip balms
Nail products: Nail polishes and enamels
SAFETY INFORMATION ABOUT YELLOW IRON OXIDE
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off contaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
