TiO₂
Titanium dioxide (rutile)
- CAS
- Formula
- TiO₂
- Refr. index
- ~2.7
Used forHiding power and whiteness in nearly every opaque coating.
Rutile grades are surface-treated to resist UV chalking. The single most important pigment in coatings.
Full profilePigments and fillers are the solid particles that give coatings color, opacity, corrosion protection, texture and body. They often make up a large share of a paint’s weight and much of its performance.
Pigments are insoluble particles chosen for an optical or protective effect. Prime pigments such as titanium dioxide scatter light to hide what is underneath; colored pigments absorb parts of the spectrum; anti-corrosive pigments such as zinc phosphate or metallic zinc protect steel chemically or sacrificially.
Fillers, also called extenders, are lower-cost minerals such as barium sulfate, talc and calcium carbonate. They add film build, control gloss and sanding, reduce cost and, in the case of platy talc or mica, form overlapping barriers that slow moisture.
The balance between solids and binder is described by pigment volume concentration (PVC). Near the critical PVC, binder can no longer fill the spaces between particles: films become porous, flat and weaker. Protective coatings are usually formulated well below CPVC.
From the TiO₂ in a white topcoat to the aluminum oxide grit in an anti-slip floor.
Used forHiding power and whiteness in nearly every opaque coating.
Rutile grades are surface-treated to resist UV chalking. The single most important pigment in coatings.
Full profileUsed forRed-oxide primers, barn and floor colors, tints.
Inexpensive, lightfast and chemically inert.
Full profileUsed forTans, earth tones and economical yellows.
Dehydrates toward red when overheated, so avoid it in high-bake systems.
Full profileUsed forJet blacks, grays and UV protection in black liners and coatings.
Tints strongly at tiny doses and absorbs UV, shielding aromatic binders.
Full profileUsed forSafety blues, greens (with yellows) and tints.
An extremely strong, lightfast organic pigment.
Full profileUsed forCorrosion-inhibiting primers for steel.
A lower-toxicity replacement for lead and chromate inhibitive pigments.
Full profileUsed forZinc-rich epoxy and inorganic zinc silicate primers.
Corrodes sacrificially to protect steel. Needs high loading and a blast-cleaned surface.
Full profileUsed forFilm build, chemical resistance and sanding in primers and floors.
A very inert, low-oil-absorption filler.
Full profileUsed forBarrier, sanding and sag resistance in primers and fillers.
Platy particles overlap like shingles, slowing moisture penetration.
Full profileUsed forSag control on vertical surfaces, anti-settling and matting.
Builds viscosity at rest that thins under shear, key for vertical polyurea and epoxy work.
Full profileUsed forBroadcast anti-slip texture in floor, deck and ramp coatings.
Hard and sharp, so it outlasts silica sand for traction.
Full profileUsed forLow-cost extender in architectural paints, sealants and roof coatings.
Dissolves in acid, so keep it out of chemical-resistant linings.
Full profileHiding power comes from light scattering, which grows with the gap between the refractive index of the pigment and that of the binder. Rutile TiO₂, at about 2.7 against roughly 1.5 for most resins, scatters light better than any other white pigment, which is why it dominates.
Dispersion is where pigments succeed or fail. Particles arrive as clumps that must be wetted by resin, broken down by high-shear mixing and kept stable by dispersing agents. Poor dispersion means weak color, low gloss and settling.
For corrosion control, barrier pigments such as talc and mica lengthen the path for water, inhibitive pigments such as zinc phosphate passivate steel, and sacrificial zinc dust corrodes in place of the steel.
The bigger the gap from the binder, the more light scatters and the better the pigment hides. Fillers sit close to the binder, so they add bulk, not opacity.
What each class contributes, and what to watch for.
| Class | Examples | Main job | Watch for |
|---|---|---|---|
| Prime white | Rutile TiO₂ | Opacity and whiteness | Cost; needs good dispersion |
| Inorganic color | Iron oxides, carbon black | Durable, economical color | Duller shades |
| Organic color | Phthalo blue and green | Bright, strong color | Price; some fade outdoors |
| Anti-corrosive | Zinc phosphate, zinc dust | Protect steel | Surface prep and loading |
| Fillers | BaSO₄, talc, CaCO₃ | Build, barrier, cost | Too much lowers performance |
| Functional | Fumed silica, Al₂O₃ | Sag control, slip resistance | Viscosity, equipment wear |
Most pigments and fillers are low-toxicity once bound in a cured film, but dry powders create dust, and some minerals and metals carry specific hazards.
Always follow the product’s Safety Data Sheet, your employer’s safety program and local regulations. This page is general reference information, not a substitute for them.
Rutile TiO₂ has a very high refractive index, about 2.7, so it scatters light more efficiently than any other white pigment. That gives excellent hiding at relatively low loadings.
Pigments are chosen for color, hiding or protection. Fillers (extenders) are lower-cost minerals that add volume, film build, barrier properties or sanding ease with little effect on color.
Pigment volume concentration is the volume of pigment and filler as a percentage of the total dry film. Above the critical PVC there is not enough binder to surround every particle, and the film becomes porous and weak.
Zinc is more reactive than iron, so when moisture reaches the steel the zinc corrodes first and protects it sacrificially. That requires high zinc loading and direct contact with blast-cleaned steel.