HX AP-16 Calcium strontium zinc phosphosilicate pigment
Anti-rust pigment
Technical Information
What Is HX AP-16 Calcium Strontium Zinc Phosphosilicate
HX AP-16 is an ultra-premium white anti-corrosion pigment featuring a quaternary Ca-Sr-Zn phosphosilicate chemistry. It combines four active metal ions — calcium, strontium, zinc, and the phosphosilicate anion — into a single, highly engineered pigment particle. This multi-cationic approach delivers broad-spectrum corrosion inhibition: calcium and strontium build a dense passivation film, zinc provides galvanic protection at exposed metal sites, and the phosphosilicate matrix ensures sustained, controlled release throughout the coating service life. With the lowest oil absorption in the series (15-29 g/100g), tightest particle size (D50: 3.0-5.0 μm), lowest water solubility (<1.0%), and all non-automotive applications rated Recommended, AP-16 represents the pinnacle of the HX anti-rust portfolio.
Key Features
- Quaternary Ca-Sr-Zn-Phosphosilicate Chemistry — Four active ions in one particle for multi-mechanism, broad-spectrum corrosion protection
- Lowest Oil Absorption in Series (15-29 g/100g) — Maximum formulation flexibility; load more pigment or reduce binder demand
- Tightest Particle Size Distribution (D50: 3.0-5.0 μm) — Narrower than all other HX grades, ensuring superior surface smoothness in thin-film coatings
- Ultra-Low Water Solubility (<1.0%) — Minimal leaching ensures long-term coating integrity even in high-humidity or immersion service
- Wide pH Tolerance (7.0-11.0) — From neutral to strongly alkaline, compatible with virtually all industrial binder systems
- Universal Recommended Rating — Validated across every non-automotive application category OEM and refinish
Recommended Applications
| Application | Suitability |
|---|---|
| Automotive OEM | ❌ Not Recommended |
| Automotive Refinish | ❌ Not Recommended |
| Industrial Paints | ✅ Recommended |
| Powder Coatings | ✅ Recommended |
| Decorative Water Base Paints | ✅ Recommended |
| Decorative Solvent Base Paints | ✅ Recommended |
| Decorative Universal Stainers | ✅ Recommended |
✅ Recommended | ⚪ Suitable | ❌ Not Recommended
Technical Data
| Physical Form | White powder |
| Oil Absorption | 15-29 g/100g |
| Water Soluble Matter | < 1.0% |
| pH Value | 7.0-11.0 |
| Sieve Residue (45 μm) | < 1.0% |
| Primary Particle Size D50 | 3.0-5.0 μm |
Packaging
25 kg/bag. Custom packaging available upon request.
Frequently Asked Questions
What makes AP-16 the top-tier grade in the HX series?
Three things set AP-16 apart: (1) the quaternary Ca-Sr-Zn-phosphosilicate chemistry delivering four corrosion inhibition mechanisms in one pigment — no other grade in the series combines more than three active elements; (2) the lowest oil absorption (15-29) and tightest particle size (D50 3.0-5.0), enabling use in the most demanding thin-film, high-gloss applications; and (3) the lowest water solubility (<1.0%), making it the only HX grade recommended without reservation for immersion service and marine coatings.
Why choose a quaternary pigment over a simpler mono- or dual-cationic grade?
Corrosion is a multi-mechanism problem — no single inhibitor addresses all failure modes. A mono-cationic phosphate (like AP-13) provides excellent passivation but limited barrier protection. A pure silicate (like AP-12) builds a great barrier but provides slower initial passivation. AP-16’s quaternary design — Ca for rapid passivation, Sr for film density, Zn for galvanic protection at scratches, and phosphosilicate for sustained release — covers all bases simultaneously. For mission-critical applications where coating failure is not an option, the incremental cost of AP-16 over simpler grades is typically recovered many times over in reduced warranty claims.
Can AP-16 be used as a direct replacement for zinc phosphate in automotive electrocoat?
AP-16 is designed as a performance upgrade over zinc phosphate, not just a replacement. Its quaternary chemistry provides equivalent or better salt spray resistance (typically 800+ hours ASTM B117 at 5% PVC) while eliminating the environmental concerns of high-zinc formulations. However, electrocoat systems have highly specific conductivity and throwing power requirements — we recommend a full compatibility trial in your specific electrocoat bath before production implementation.
Disclaimer — This Technical Data Sheet reflects our best understanding of typical product properties at the time of publication. Listed values are representative of standard production and are not intended as specifications, contractual parameters, or fitness guarantees. Batch variations within normal manufacturing tolerances may occur; users should verify critical parameters against their own requirements before use. Processing methods, formulations, and end-use environments are beyond the manufacturer’s control. The buyer assumes full responsibility for confirming product suitability through its own testing and quality assurance. No intellectual property license is granted or implied. All warranties are disclaimed, including merchantability and fitness for a particular purpose. The manufacturer is not liable for incidental, consequential, or special damages. All sales are governed by the manufacturer’s standard terms, available upon request. This product may contain particles below 0.1 μm.