Water-borne inorganic zinc-rich primer binder
Inorganic zinc-rich primers protect steel the same way galvanising does: the zinc corrodes in place of the steel. A water-borne lithium silicate binder gives the same protection with no solvent and no VOC.
How an inorganic zinc-rich primer protects steel
The dry film is mostly metallic zinc dust held in an inorganic silicate matrix. Because the zinc particles touch each other and the steel, they form a galvanic cell in which the zinc is the anode and corrodes first. The silicate binder cures into an inorganic film that bonds to the blasted steel surface. The result resists solvents, weathering, heat, and wet–dry cycling.
Two binders, two starting points
| GHSL | GHSL-Ⅲ | |
|---|---|---|
| Type | Lithium silicate solution, modulus 2.5–4.8 made to order | Modified lithium silicate with better film formation |
| pH | ≈ 11 | 11.5–12.5 |
| Starting ratio, binder : zinc | 3 : 7 (400–500 mesh zinc) | 3 : 7 (400 mesh zinc) |
| Best for | Formulators who want to tune the modulus and build their own system | A ready-designed two-component primer binder |
GHSL-Ⅲ primer performance (manufacturer test data)
| Salt spray | 8000 h | Hardness | 6H |
|---|---|---|---|
| Damp heat | 3000 h | Adhesion (circle method) | Grade 1 |
| Water resistance | 8000 h | Impact | 55 cm |
| Heat resistance | 450 °C | Dry time, 25 °C | touch 8 min · hard 6 h |
Mixing and use: two-component. Allow 30 minutes induction after mixing and use within 4 hours. Apply by spray, brush or roller.
Choosing a binder: lithium silicate vs. alternatives
| Lithium silicate (water-borne) | Potassium silicate (water-borne) | Ethyl silicate (solvent-borne) | |
|---|---|---|---|
| VOC | None | None | Solvent-borne |
| Cure | Self-curing | Self-curing | Moisture cure (hydrolysis) |
| Flammability in storage | Non-flammable | Non-flammable | Flammable |
| Notes | Lower tendency to efflorescence; film insoluble once cured | Widely used; typically more prone to efflorescence than lithium silicate | Established system; tolerant of lower temperatures, but needs adequate humidity to cure |
Application notes
- Surface preparation. Inorganic zinc primers need abrasive-blasted steel, typically to Sa 2½ with a sharp profile. Follow the specification of your coating system.
- Mixing. Add zinc dust to the binder under agitation and keep stirring during application so the zinc stays suspended.
- Pot life. Use the mixed GHSL-Ⅲ primer within 4 hours.
- Topcoating. Inorganic zinc films are porous, so a mist coat or tie coat is normally used before organic topcoats.
Starting formulations are guidance only and are not suitable for every application. Trial the product in your own system before production use.
Frequently asked questions
What binder-to-zinc ratio should I start with?
How long can a lithium silicate zinc-rich primer protect steel?
Is the binder VOC-free?
Can you make lithium silicate at a specific modulus?
Need the full TDS or a trial sample?
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