Aluminum Oxide Blast Media: Properties & Uses
Normal corundum is a reusable blasting agent made from α-aluminum oxide. This sharp-edged blasting agent is versatile and, thanks to its titanium oxide content, slightly tougher and more durable than high-purity precious corundum. It has exceptional hardness; it is the fourth hardest material after diamond.
Aluminum oxide blast media: properties, types and applications
Its high hardness and abrasive action make it suitable for intensive surface cleaning, roughening, and the removal of coatings and contaminants.
Different types are distinguished by their composition and purity. Common variants include brown fused alumina, white fused alumina and pink fused alumina.
What is corundum?
Corundum is crystalline aluminum oxide (Al₂O₃). As a blasting abrasive, it is characterized by its high hardness, angular grain shape and strong abrasive action.
When the grains strike the workpiece surface, their sharp edges produce an intensive cleaning and roughening effect. This makes aluminum oxide particularly suitable for blasting applications that require a high material removal rate or a pronounced surface profile.
With a Mohs hardness of 9, corundum is among the hardest mineral materials.
What types of aluminum oxide blast media are available?
Aluminum oxide abrasives differ primarily in their purity and chemical composition. These differences affect toughness, resistance to breakdown and suitability for different applications.
Brown fused alumina
Brown fused alumina is an angular aluminum oxide abrasive with an Al₂O₃ content of approximately 94–96%. Its titanium oxide content makes it somewhat tougher and more durable than high-purity fused alumina.
Its high hardness and abrasive action make it a versatile blast medium for intensive cleaning and roughening.
White fused alumina
White fused alumina contains more than 99.7% aluminum oxide and is virtually iron-free. It is very hard, brittle and sharp-edged, with a strong cutting and grinding action.
It is used particularly where intensive blasting performance must be combined with high abrasive purity or virtually iron-free media.
Pink fused alumina
Pink fused alumina contains more than 99.3% aluminum oxide. Added chromium oxide gives it its characteristic color and makes it somewhat tougher and more resistant to breakdown than white fused alumina.
Pink fused alumina is also virtually iron-free and highly abrasive.
Brown, white or pink fused alumina?
| Property | Brown fused alumina | White fused alumina | Pink fused alumina |
|---|---|---|---|
| Color | Brown/gray-brown | White | Pink |
| Al₂O₃ | 94–96% | >99.7% | >99.3% |
| Hardness | Mohs 9 | Mohs 9 | Mohs 9 |
| Grain shape | Angular/splintery | Angular/splintery | Angular/splintery |
| Key characteristic | Somewhat tougher due to TiO₂ | High purity, virtually iron-free | Virtually iron-free, somewhat tougher than white alumina |
| Blasting action | Highly abrasive | Highly abrasive | Highly abrasive |
What is aluminum oxide used for in abrasive blasting?
Typical applications
- Cleaning and roughening
- Rust and scale removal
- Paint and coating removal
- Deburring and edge rounding
- Matting
Typical workpiece materials
- Low- and high-alloy steels
- Non-ferrous metals
- Concrete and natural stone, ceramics
- Plastics and composite materials
- Glass and wood
What grit sizes are available for aluminum oxide?
Aluminum oxide is available in a range of grit sizes. Together with blasting pressure, stand-off distance, impact angle and the workpiece, grit size influences the effect on the surface and the resulting finish.
Brown, white and pink fused alumina are classified using systems including FEPA grit designations. Our technical documentation specifies the following principal grain size ranges for these three types:
| FEPA | Principal grain size range |
|---|---|
| F12 | 1,400–2,000 µm |
| F14 | 1,180–1,700 µm |
| F16 | 1,000–1,400 µm |
| F20 | 850–1,180 µm |
| F24 | 600–850 µm |
| F30 | 500–710 µm |
| F36 | 425–600 µm |
| F40 | 355–500 µm |
| F46 | 300–425 µm |
| F54 | 250–355 µm |
| F60 | 212–300 µm |
| F70 | 180–250 µm |
| F80 | 150–212 µm |
| F90 | 125–180 µm |
| F100 | 106–150 µm |
| F120 | 90–150 µm |
| F150 | 63–106 µm |
| F180 | 53–90 µm |
| F220 | 45–75 µm |
What happens to aluminum oxide during blasting?
Aluminum oxide is hard but also brittle. Repeated impacts on the workpiece surface cause the grains to fracture into smaller fragments that retain sharp edges.
This maintains the abrasive action, while the media becomes progressively finer with use. Worn material must be removed from the media circuit and replaced with fresh abrasive.
How does aluminum oxide change during blasting?
Images from the VULKAN INOX test center show brown fused alumina before use and after several blasting cycles at 5 bar. As the number of cycles increases, progressive grain breakdown becomes visible: the abrasive fragments and the proportion of smaller particles increases.