Casting Coatings Low Sodium White Corundum 325 mesh for Precision Casting Coating
Product Overview
Low Sodium White Corundum 325 mesh is a high-purity (Al₂O₃≥99%), low-sodium (Na₂O≤0.1%) fine alumina powder, specially designed for water-based silica sol casting coatings in precision casting (investment casting, lost foam casting). Its superior high-temperature resistance, chemical stability, and uniform particle size significantly improve surface finish and reduce metal penetration or sand adhesion defects.
Key Advantages
1. High Purity & Low Sodium Content
- Al₂O₃≥99%: Minimizes chemical reactions with molten metal, preventing surface pores and inclusions.
- Na₂O≤0.1%: Eliminates sodium-induced destabilization of silica sol, extending coating shelf life.
2. Precise Particle Size (325 mesh, D50≈45μm)
- Uniform distribution ensures dense, defect-free coatings, achieving surface roughness Ra≤3.2μm.
- Excellent compatibility with silica sol, enhancing suspension stability and preventing sedimentation.
3. Exceptional Thermal Performance
- Melting point: 2050°C, inert to molten steel, aluminum, and nickel-based alloys.
- Low thermal expansion (8.0×10⁻⁶/°C), preventing cracking during high-temperature pouring.
Applications in Precision Casting
1. Coating Formulation (Typical Recipe)
- Primary Layer Coating Example
- Benefits: High coating strength, crack-free drying, and easy shell removal.
2. Recommended Processes
- Investment Casting: Ideal for turbine blades, aerospace components, and high-end castings.
- Lost Foam Casting: Enhances surface quality of iron/steel castings, reducing post-machining.
3. Performance Comparison
| Property | Low Sodium White Corundum | Zircon Flour | Quartz Powder |
|---|---|---|---|
| Max. Temperature | 2050°C | 1540°C (sinters) | 1713°C (phase change) |
| Thermal Stability | Excellent | Good | Poor (high expansion) |
| Surface Finish | Smooth, no penetration | Micro-cracks risk | Rough texture |
Usage Guidelines
- Dispersion: Pre-mix with silica sol, then high-speed stir (≥1200 rpm, 20 mins).
- Coating Thickness: Apply 20~40μm per layer (spray/dip), fully dry between layers.
- Eco-Friendly: Heavy-metal-free, compliant with foundry environmental standards.
Conclusion
Low Sodium White Corundum 325 mesh is the optimal filler for water-based silica sol coatings, delivering high-definition surfaces and reduced scrap rates in precision casting. A cost-effective alternative to zircon flour for premium-grade castings.
