Loaded at 2 – 8 wt% as a UV-A and UV-B absorber in clear and pigmented exterior systems. Extends film life on wood substrates and weather-exposed acrylic / polyurethane topcoats. Often combined with TiO₂ for UV-B coverage and HALS for radical scavenging.

5 – 15 wt% ZnO in zinc-rich epoxy and inorganic zinc silicate primers (paired with 60 – 85% zinc dust). ZnO functions as both a sacrificial pigment and a binder modifier, smoothing pot-life and improving topcoat adhesion.

1 – 3 wt% ZnO in 100% acrylic and acrylic-silicone exterior emulsions. Active against algae, mildew, and common wood-rot fungi. Combine with isothiazolinone or zinc pyrithione for synergistic effect.

0.5 – 2 wt% as flow modifier and pH buffer in polyester and epoxy powder coatings. Silane-treated grade preferred — untreated ZnO can absorb moisture during storage and reduce powder flowability.

Silane (vinyl, amino, or epoxy-silane) is preferred when the coating cures by silane condensation or when chemical bonding to silica fillers is desired (1K silicone, hybrid systems). Stearic acid is cheaper and better for non-polar systems (solvent-borne alkyd, polyolefin powder coating). For waterborne acrylic — silane is the safer default.

D50 0.3 – 1 μm with D90 ≤ 3 μm allows direct disc-blade dispersion in low- to medium-viscosity systems. For high-gloss topcoats requiring D50 < 0.5 μm in-film, pre-disperse in a bead mill to reach Hegman 7+ fineness.

Nano-ZnO (D50 < 100 nm) is transparent — required when film clarity matters (clear wood coatings, automotive clears). Standard coating-grade ZnO (D50 ~ 0.5 μm) is opaque and provides full coverage at lower cost. For exterior wall paints and primers, standard grade is the cost-performance choice.

In most acrylic and polyurethane systems — yes. Verify wet adhesion and recoat behavior on a 5 wt% pilot before full-scale switch. Surface-treated grades may shift viscosity and require a small (5 – 10%) dispersant adjustment.