White Fused Alumina (WFA) and Brown Fused Alumina (BFA) are both synthetic abrasives made from bauxite but differ in composition, properties, and applications due to variations in their manufacturing processes and purity levels.
1. Raw Material & Manufacturing Process
White Fused Alumina (WFA):
Made from high-purity calcined alumina (Al₂O₃ > 99%).
Produced in an electric arc furnace at temperatures above 2000°C, followed by slow cooling to form large crystals.
No additives; pure white color due to minimal impurities.
Brown Fused Alumina (BFA):
Made from bauxite (containing ~85-90% Al₂O₃) with added carbon (coke) and iron filings.
Smelted in a reduction process in an electric arc furnace, where impurities (SiO₂, Fe₂O₃, TiO₂) are partially removed.
Brown color due to residual impurities (e.g., titanium oxide, silica).
2. Chemical Composition
| Property | White Fused Alumina (WFA) | Brown Fused Alumina (BFA) |
|---|---|---|
| Al₂O₃ Content | ≥ 99% | 94–97% |
| SiO₂ | < 0.2% | 1–2% |
| Fe₂O₃ | < 0.1% | 0.1–0.5% |
| TiO₂ | Trace | 1.5–3.5% |
3. Physical Properties
| Property | WFA | BFA |
|---|---|---|
| Hardness (Mohs) | 9.0 | 8.5–9.0 |
| Toughness | Lower (more brittle) | Higher (tougher) |
| Crystal Structure | Large, blocky crystals | Smaller, sharper grains |
| Melting Point | ~2050°C | ~1850–1900°C |
4. Key Differences
Purity: WFA is purer (≥99% Al₂O₃), while BFA contains more impurities.
Color: WFA is white; BFA is brown due to TiO₂ and other oxides.
Hardness vs. Toughness: WFA is harder but more brittle; BFA is slightly softer but tougher and more impact-resistant.
Cost: WFA is more expensive due to high-purity raw materials.
5. Applications
White Fused Alumina:
Precision grinding (e.g., automotive, aerospace).
High-quality sandpaper, abrasive tools, and polishing compounds.
Refractory materials for high-temperature applications.
Ceramics and electronics (due to high purity).
Brown Fused Alumina:
Heavy-duty grinding, blasting, and cutting (e.g., steel, metalworking).
Sandpaper, grinding wheels, and bonded abrasives.
Refractories for furnaces and kilns.
Anti-slip surfaces (e.g., flooring, coatings).
6. Which to Choose?
Choose WFA for high-precision, fine-finishing tasks where purity and hardness are critical.
Choose BFA for rough grinding, heavy material removal, or cost-sensitive applications requiring toughness.