SZ-2 (Zirconium Ammonium Carbonate, Bacote 20 Equivalent): The Aqueous-Stable Zirconate for Waterborne Paint Adhesion and Paper Coating
SEMITECH SZ-2 is the waterborne zirconium ammonium carbonate — Bacote 20 equivalent — uniquely stable in aqueous formulation. Used at 0.2–0.6 wt% on resin solids in waterborne metal primers, paper coating, and salt-spray-uplift applications. 25 kg HDPE jerrycan, no refrigeration required.
Contents
| ~20% | 0.2–0.6% | 240→500+ hr |
|---|---|---|
| ZrO₂ in solution | Typical loading | Salt-spray uplift |
Chemistry & Specifications
Aqueous zirconium ammonium carbonate complex; pH 8.5–9.5; uniquely water-stable Zr species.
SZ-2 is an aqueous Zr(IV) complex stabilised by carbonate-ammonium ligands, supplied at 20% Zr (as ZrO₂), pH 8.5–9.5, density 1.30–1.35 g/cm³, chloride ≤500 ppm. The only commercially-significant zirconate genuinely stable in water for 6–12 months.
Functionally equivalent to MEL Chemicals Bacote 20 at ~40% landed-cost discount for Asia-Pacific formulators.
Coupling Mechanism: Aqueous Zr-OH Adsorption + Drying-Triggered ZrO₂ Deposition
Zr-carbonate adsorbs to substrate surface; on drying, NH₃ + CO₂ release leaves ZrO₂ crosslink layer.
- Loading 0.2–0.4% Zr on resin solids — waterborne 1K acrylic metal primer; 240→400 hr salt-spray uplift
- Loading 0.4–0.6% Zr on resin solids — high-performance waterborne primer; 500+ hr salt-spray rating
- Loading 0.05–0.2% on resin solids — paper coating crosslinker for starch and PVOH binders
The salt-spray uplift is the commercial value driver: 240→500+ hours at 0.4% Zr on solids, at 1.5–3% of finished paint cost. Compatibility: works with acrylic, alkyd, PU, and epoxy waterborne binders at pH 7.5–10.5; below pH 7, Zr-carbonate precipitates.
▶Show full content (5 sections)
Applications & Formulation Guidance
Waterborne metal primers (largest), paper coating crosslinker, leather treatment, paperboard packaging.
Waterborne metal primer adhesion promoter is the largest application — 1K acrylic/alkyd primers for steel, galvanised steel, aluminium, and zinc substrates. Salt-spray uplift positions standard architectural primer as industrial-grade. DTM waterborne coatings at 0.3–0.5% replace primer + topcoat with single-coat systems.
Paper coating crosslinker at 0.05–0.2% improves wet-strength and grease resistance for food packaging. Leather tanning auxiliary at 1–3% on leather weight. Glassfibre sizing at 0.1–0.3% Zr for improved wet-out.
Procurement, Storage and Quality Control
CoA per shipment; 25 kg HDPE; tolerates ambient humidity; 12-month shelf life; non-flammable aqueous solution.
Standard packing 25 kg HDPE jerrycans; 200 kg drums for bulk paint plants. MOQ 25 kg. Lead time 1 week to Asia, 4–6 weeks to Europe/North America. No N₂ blanket needed; non-flammable. Avoid freezing. Maintain paint pH 7.5–10.5. Pricing: CNY 32,000–40,000/MT vs Bacote 20 at USD 7–10/kg — 35–45% discount.
SZ-2 Specification Sheet
SEMITECH stocked grade; CoA per batch.
| Property | Specification | Test Method |
|---|---|---|
| Chemical name | Zirconium ammonium carbonate (aqueous solution) | — |
| Synonyms | AZC / Bacote 20 equivalent / Zr-AC | — |
| Form | Aqueous solution | — |
| ZrO₂ content | 19.5–20.5% | Gravimetric ignition |
| Active Zr species | (NH₄)₂[Zr(OH)₂(CO₃)₂]·H₂O cluster | — |
| pH (20°C) | 8.5–9.5 | pH meter |
| Density (20°C) | 1.30–1.35 g/cm³ | ASTM D1475 |
| Total NH₃ | 11–13% | Kjeldahl |
| Chloride content | ≤500 ppm | Mohr titration |
| Appearance | Clear to slightly hazy aqueous solution | Visual |
| Viscosity (25°C) | 5–15 cP | Brookfield |
| Flammability | Non-flammable (aqueous) | — |
| Storage temperature | 5–30°C; avoid freezing | — |
| Packaging | 25 kg / 200 kg HDPE | — |
| Shelf life | 12 months sealed below 30°C | — |
FAQ
+My waterborne primer with SZ-2 develops a fine sediment on storage — is it still usable?
Sediment indicates pH drift below 7.5. Re-disperse, add 0.05–0.10% ammonia or AMP-95 to restore pH 8.5–9.5, and verify with a crosslink test. Prevention: improve seal integrity, use pH-compatible pigments, add biocide.
+Can I add SZ-2 to a solvent-borne paint formulation?
No — SZ-2 phase-separates in solvent-borne systems. Use SZ-AcAc (zirconium acetylacetonate) at 0.3–1.0% for solvent-borne adhesion promotion.
+Is the salt-spray uplift on cold-rolled steel really 240→500+ hours from 0.4% SZ-2?
Yes — independently verified. SZ-2 deposits a 1–5 nm ZrO₂ passivation layer at the metal-paint interface. Requires proper substrate cleaning, 25 µm minimum film thickness, 7-day cure before testing, and compatible binder (styrene-acrylic gives strongest uplift).