Titanium dioxide (rutile)
The most important pigment in coatings. Rutile TiO₂ scatters light more strongly than any other white pigment, giving paints their hiding power.
Titanium dioxide pigment is produced in two crystal forms, rutile and anatase. Coatings overwhelmingly use rutile, with a refractive index around 2.7, which is milled to a particle size near 0.2–0.3 µm, about half the wavelength of visible light, to maximize scattering.
TiO₂ provides whiteness and opacity in almost every opaque coating, from latex wall paint to polyurea and epoxy floor coatings, and it is the base for most light and pastel colors. In polyurea and polyurethane systems it is dispersed in the B-side.
Hiding comes from the large refractive-index gap between TiO₂ (about 2.7) and typical binders (about 1.5). Untreated TiO₂ is photoactive and can accelerate binder breakdown under UV, so pigment grades for coatings carry inorganic surface treatments (such as alumina, silica or zirconia) that reduce chalking and improve dispersion.
TiO₂ is chemically inert, but fine powder creates dust; use local exhaust and particulate respirators when handling dry pigment. Regulatory classification of TiO₂ powder has been debated in the EU, so check current SDS and regulations.
Coatings use rutile almost exclusively because it scatters light better and is less photoactive, so it chalks less outdoors.
UV can activate TiO₂ and degrade the surrounding binder. Surface-treated, durable rutile grades and UV-stable binders minimize chalking.
