Aqueous zirconium ammonium carbonate complex; pH 8.5–9.5; uniquely water-stable Zr species.

SZ-2 — zirconium ammonium carbonate, Bacote 20 commercial-name equivalent — is an aqueous-stable Zr(IV) complex formed from zirconium oxychloride, ammonium carbonate, and ammonia. The active species is a hydroxo-carbonato-Zr cluster stabilised in solution by ammonium counterions and excess carbonate; molecular formula commonly written as (NH₄)₂[Zr(OH)₂(CO₃)₂]·H₂O though the actual species is a mixture of mononuclear and oligomeric clusters. SEMITECH supplies SZ-2 as a clear-to-slightly-hazy aqueous solution at 20% Zr (calculated as ZrO₂) with pH 8.5–9.5, density 1.30–1.35 g/cm³ at 20°C, ammonia content ~12% (free + bound), and chloride content ≤500 ppm.

SZ-2 is the only commercially-significant zirconate that is genuinely stable in aqueous formulation — bare alkoxide zirconates (SZ-TPZ, SZ-12) hydrolyse in water within minutes; chelated zirconates (SZ-AcAc) are stable for hours but not days at high water content. SZ-2 remains stable in waterborne paint formulations for 6–12 months thanks to the carbonate-ammonium ligand stabilisation, which is gradually displaced during paint dry-down by atmospheric CO₂ loss + pH drop, releasing active Zr species into the dried film. Functionally and commercially equivalent to MEL Chemicals Bacote 20 (the original commercial-name reference); SEMITECH SZ-2 provides the cost-rational sourcing alternative for Asia-Pacific waterborne paint formulators at ~40% landed-cost discount.

Zr-carbonate adsorbs to substrate surface; on drying, NH₃ + CO₂ release leaves ZrO₂ crosslink layer.

In waterborne metal primer applications, SZ-2 functions both as an adhesion promoter (binding the polar acrylic or alkyd binder to the metal substrate) and as a film crosslinker (depositing a ZrO₂ network on drying that links binder polymer chains via Zr-O-C ester bonds). The mechanism: Zr-carbonate clusters in the wet paint film adsorb electrostatically to the metal surface (zinc, aluminium, cold-rolled steel) via their hydroxide-rich coordination sphere; on drying, ammonia and carbon dioxide volatilise, the pH drops, and the carbonate ligands release, leaving Zr-OH and Zr-O-substrate bonds on the metal surface and Zr-O-binder bonds in the bulk film.

• 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 effect is the commercial value driver: a typical waterborne acrylic 1K metal primer rates 240 hours ASTM B117 salt-spray (loss-of-adhesion criterion) without zirconate; with SZ-2 at 0.4% Zr on solids, the same primer rates 500–800 hours. In a marketplace where 500-hour rating is the threshold for premium pricing on industrial machinery, agricultural equipment, and HVAC enclosure paints, the SZ-2 cost premium (typically 1.5–3% of finished paint cost) is recovered many-fold by the price step-up. Compatibility: SZ-2 is compatible with most acrylic, alkyd, polyurethane, and epoxy waterborne binders in the pH range 7.5–10.5; below pH 7, Zr-carbonate destabilises and the catalyst falls out of solution as ZrO(OH)₂ precipitate.

Waterborne metal primers (largest), paper coating crosslinker, leather treatment, paperboard packaging.

Waterborne metal primer adhesion promoter is the largest application — 1K acrylic and alkyd primers for cold-rolled steel, hot-dip galvanised steel, aluminium, and zinc-rich substrates use SZ-2 at 0.2–0.6% Zr on resin solids. The salt-spray uplift (240→500+ hours ASTM B117) translates directly to product positioning: standard architectural primer becomes industrial-grade primer; standard agricultural-machinery primer qualifies for high-corrosion environment use. Direct-to-metal (DTM) waterborne acrylic coatings for HVAC equipment, fence post coatings, and outdoor furniture use SZ-2 at 0.3–0.5% as both adhesion promoter and crosslinker, allowing a single-coat application to replace primer + topcoat systems.

Paper coating crosslinker for printable coated paper, packaging paperboard, and corrugated board uses SZ-2 at 0.05–0.2% on coating-binder solids to crosslink starch, PVOH, and acrylic binders during drying ovens. The crosslink improves wet-strength, water resistance, and grease resistance — important for food packaging board and folding-carton applications. Leather treatment as a tanning auxiliary at 1–3% on leather weight provides supplementary tannage compatible with chrome and chrome-free systems. Glassfibre sizing for short-glass thermoplastics uses dilute SZ-2 (0.1–0.3% Zr) as one component of a multi-functional size to improve wet-out in subsequent compounding.

CoA per shipment; 25 kg HDPE; tolerates ambient humidity; 12-month shelf life; non-flammable aqueous solution.

SEMITECH issues a CoA on every batch with: ZrO₂ content (gravimetric ignition, target 19.5–20.5%), pH (target 8.5–9.5), density at 20°C, ammonia content (Kjeldahl, total NH₃ + NH₄⁺), chloride content (Mohr titration, target ≤500 ppm), and visual appearance. Standard packing is 25 kg HDPE jerrycans; 200 kg HDPE drums for bulk paint plants. MOQ 25 kg per grade. Lead time 1 week to Asia gateway ports for stocked grade, 4–6 weeks to Europe and North America after sea freight.

Storage: SZ-2 is uniquely tolerant of ambient handling among zirconates — no nitrogen blanket required, ambient humidity has no effect on the catalyst, no flammability concern (aqueous solution; non-flammable; UN classification non-hazardous for air freight). Recommended: store sealed below 30°C; freezing should be avoided (Zr-carbonate destabilises on freeze-thaw cycles, may precipitate). Shelf life 12 months sealed; opened drums consumable within 6 months. pH compatibility: maintain finished waterborne paint pH between 7.5 and 10.5; below pH 7, zirconate destabilises; above pH 11, ammonia is lost rapidly causing premature crosslinking. Monitor paint pH on tank-storage during production; readjust with ammonia or amine if drift occurs. Cost positioning: SZ-2 Q1 2026 ex-Zhejiang spot CNY 32,000–40,000/MT (USD 4.5–5.6/kg); MEL Chemicals Bacote 20 distributor pricing North America USD 7–9/kg, Europe USD 8–10/kg landed — 35–45% landed-cost discount for SEMITECH supply. Health: alkaline aqueous solution; mild skin and eye irritant. Standard PPE — nitrile gloves and splash goggles. SDS in EU/GHS format issued with every shipment.

SZ-2 is the only aqueous-stable zirconate — Bacote 20 equivalent for waterborne paints, paper coating, and leather treatment. 240→500+ hr salt-spray uplift on metal primers at 0.2–0.6% Zr loading. No nitrogen blanket needed; ambient handling. ~40% landed-cost discount vs MEL Bacote 20 for Asia-Pacific formulators.

SEMITECH stocked grade; CoA per batch.