product
Aluminum oxide
AO LINE · AGGRESSIVE CUT
High-hardness synthetic mineral abrasive for anchor profile without ferrous contamination
CYM Materiales supplies aluminum oxide (alumina), a synthetic mineral abrasive produced from bauxite, available in two grades according to purity —brown with 95.8 % Al₂O₃ for general industrial use and white with 99.7 % Al₂O₃ for high-purity applications— and in twelve standard grit sizes from grit 14 (1.18–1.70 mm) to grit 220 (0.05–0.07 mm). It is the reference abrasive for surface preparation with high anchor profile without ferrous contamination, paint and oxide stripping, and blasting of non-ferrous metals where the extreme hardness of the medium and the absence of free iron are process requirements.
Unlike metallic shot that works by impact and glass beads that work by soft impact, aluminum oxide works by aggressive cutting: its Mohs hardness of 9 —just below diamond— and its sharp edges allow removal of oxides, mill scale, paint, heat treatment salts and hardened coatings from any metallic substrate. Its very low free iron oxide content (0.3 % in brown, 0.01 % in white) makes it especially suitable for blasting stainless steel, aluminum, titanium, bronze, brass and zamak, where ferrous contamination would generate later oxidation spots.
Aluminum oxide is used exclusively in compressed air systems —manual blast rooms, cabinets and pressure or suction blast rooms—; it is not used in centrifugal wheel equipment due to its highly abrasive nature, which would generate accelerated wear on blades and liners. It is chemically stable, contains no crystalline free silica, no carcinogenic or toxic components, and its service life of 10 to 40 cycles per particle offers a favorable operating cost balance compared to single-use natural mineral abrasives such as garnet or copper slag.
If your application requires a specific recommendation —including the choice between brown and white grades according to sector and required purity—, our technical team advises on the most suitable grit and grade.
APPLICATIONS
Uses and processes with aluminum oxide
Aluminum oxide is used exclusively in compressed air systems —manual blast rooms, blast cabinets and pressure or suction blast rooms—, where the operator controls angle, distance and flow through the nozzle to combine the high anchor profile provided by alumina with the absence of ferrous contamination characteristic of its composition. The choice of grade (brown for general industrial use, white for high-purity applications) and grit (#14 to #220) depends on the part, the substrate, the desired finish and the application sector.
SURFACE PREPARATION AND STRIPPING
- Brown grade in grits #24 to #80 for preparation prior to paint, epoxy coatings and powder coatings on carbon and stainless steel
- Stripping of old paint, lacquers, oxides, mill scale and combustion residues on all types of metals
- Removal of heat treatment salts and weld cleaning on stainless steel, aluminum and titanium parts
- Blasting of non-ferrous metals (bronze, brass, aluminum, zamak, titanium) without risk of free iron contamination
- Generation of uniform high anchor profile with lower consumption and better cost/treated-surface ratio than garnet or copper slag
- Suitable for large-format blast rooms with media recovery and recycling systems
PRECISION AND HIGH-PURITY APPLICATIONS
- White grade in grits #80 to #220 for sectors requiring total absence of impurities: pharmaceutical, food, medical and electronics industries
- Blasting of medical implants, surgical instruments and precision components in titanium and stainless steel
- Decorative matte finish on stainless steel, anodized aluminum and high-end alloys
- Engraving and matte finishing of glass, marble, granite and natural stone with protective masks
- Defect correction, part pretreatment and controlled roughness increase on delicate substrates
- Compatible with manual cabinets and small enclosures for low-volume, high-precision work
TECHNICAL SPECIFICATIONS
Manufacturing process and composition
Aluminum oxide is manufactured as a synthetic mineral abrasive through the electrothermal fusion of bauxite —a natural mineral rich in aluminum hydroxides— in electric arc furnaces at temperatures above 2,000 °C, followed by a controlled process of crystallization, cooling, crushing and granulometric classification. The result is a synthetic crystalline substance of high purity, with hardness very close to diamond and natural sharp edges. CYM Materiales supplies two grades differentiated by purity level and application sector:
| Compound | Brown aluminum oxide | White aluminum oxide |
|---|---|---|
| Aluminum oxide (Al₂O₃) | 95,8 % | 99,7 % |
| Silicon dioxide (SiO₂) | 1,1 % | 0,03 % |
| Iron oxide (Fe₂O₃) | 0,3 % | 0,01 % |
| Titanium dioxide (TiO₂) | 1,7 % | 0,01 % |
| Sodium oxide (Na₂O) | 0,02 % | 0,2 % |
| Calcium + magnesium oxide (CaO + MgO) | 0,3 % | 0,04 % |
The brown grade contains approximately 1.7 % titanium dioxide (TiO₂), responsible for its characteristic color and a slightly higher toughness that provides better impact resistance and longer service life on hard substrates. The white grade contains practically no TiO₂ or Fe₂O₃ —its total impurity content does not exceed 0.3 %—, making it required in sectors where cross-contamination with titanium or free iron is prohibited by standard (pharmaceutical, food, electronics, medical implants). Neither grade contains crystalline free silica, carcinogenic or toxic components, allowing handling under standard respiratory protection measures against industrial dust.
Structure and physical properties
Synthetic aluminum oxide has a hexagonal rhombohedral crystalline structure of the corundum type (α-Al₂O₃), the same crystalline phase as natural mineral corundum and the gemstones sapphire and ruby. This structure, combined with a mechanical crushing process after electrothermal fusion, produces a grain with sharp edges, high wear resistance and controlled fracture by conchoidal breaking during use, which maintains active edges as the particle reduces in size until reaching the recyclability limit. The physical properties relevant for selection and operation are the following:
| Property | Value | Standard or method |
|---|---|---|
| Crystalline structure | α-Al₂O₃ (hexagonal corundum) | X-ray diffraction |
| Grain shape | Angular with sharp edges | Microscopic inspection |
| Hardness | 9 | Mohs scale |
| Hardness | 1.800 – 2.000 | Knoop (HK) |
| Specific gravity | ~ 3,95 g/cm³ | — |
| Apparent density | 1.5 – 1.9 g/cm³ | Depending on grit size |
| Color | Dark brown / Translucent white | Brown / white grade |
| Recyclability | 10 – 40 cycles per particle | Depending on system and application |
| Crystalline free silica | Absent | Certified composition |
| Standard packaging | 25 kg bags | — |
The Mohs hardness 9 of aluminum oxide is the highest in the CYM Materiales catalog of blasting abrasives —only surpassed by diamond (Mohs 10)—, well above glass beads (Mohs 5-6), garnet (Mohs 7.5-8) and copper slag (Mohs 7-7.5). This extreme hardness, combined with the angular grain geometry and conchoidal fracture that keeps the edges active throughout media life, explains the characteristic aggressive cutting behavior of the product and its ability to generate high anchor profiles on steels and non-ferrous metals with lower consumption than natural mineral abrasives. Apparent density varies by grit size: fine grits (#150-#220) show higher values due to better packing, while coarse grits (#14-#36) show lower values. Recyclability of 10 to 40 cycles is notably higher than glass beads (5-8 cycles) and intermediate compared to metallic shot (hundreds of cycles).
Granulometry — grits #14 to #100
Aluminum oxide is classified by grit number according to the industrial standard scale for abrasives, in a nomenclature where the number indicates the nominal passing sieve expressed in mesh: a lower grit number corresponds to coarser particles and a higher number to finer particles. The standard line covers twelve grit sizes from grit #14 (1.18–1.70 mm, very coarse for aggressive anchor profile) to grit #220 (0.05–0.07 mm, fine abrasive powder for decorative matte and precision finishing). CYM Materiales supplies the complete range in both grades —brown and white— and, given the nature of the classification process, allows special grit sizes outside the standard line on request:
| Grano (mesh) | Tamaño (mm) | Aplicación característica |
|---|---|---|
| #14 | 1,18 – 1,70 | Aggressive stripping, coarse mill scale removal, deep anchor profile |
| #24 | 0,60 – 0,85 | Surface preparation, paint stripping, high anchor profile |
| #46 | 0,30 – 0,42 | Stainless and aluminum cleaning, medium profile |
| #80 | 0,15 – 0,21 | Fine finish, blasting of titanium and medical implants |
| #100 | 0,10 – 0,15 | Decorative matte, engraving of glass and natural stone |
Grit numbering follows the FEPA-F scale (Federation of European Producers of Abrasives) for blasting abrasives, equivalent to the ANSI B74.18 scale used in North America. The table shows the grits of greater industrial use; CYM Materiales additionally supplies intermediate grits #36 (0.42–0.60 mm), #54 (0.25–0.35 mm) and #60 (0.21–0.30 mm) for specific applications, and fine grits #120, #150, #180 and #220 (0.05–0.12 mm) for precision sectors, electronics and satin matte finishing. Both grades —brown and white— are available across the full range, although industrial practice concentrates the brown grade in coarse-to-medium grits (#24-#46) and the white grade in fine grits (#80-#100). Additional special grit sizes (#320, #400, micronized powders) are available on request. For the complete dimensional tolerance matrix, download the technical datasheet in PDF.
ALUMINUM OXIDE SELECTION BY APPLICATION
Which application do you need to perform?
The table shows the grit and grade (brown or white) most commonly used for each application, according to industrial practice. It is not a prescriptive rule: most applications accept more than one valid grit, and the choice between brown and white depends on the sector and the purity required by the substrate. The final selection depends on the available equipment, the part to be treated, the desired finish and the process specifications. For applications in regulated sectors (pharmaceutical, food, medical, electronics), consult our technical team for a specific recommendation.
| Application | Coarse (#14–#24) | Medium (#36–#54) | Fine (#60–#80) | Very Fine (#100+) | Brown | White |
|---|---|---|---|---|---|---|
| Aggressive stripping of mill scale, oxide and heavy crusts | ✓ | ✓ | ||||
| Stripping of paints, lacquers and hardened coatings | ✓ | ✓ | ✓ | |||
| Surface preparation prior to paint and epoxy | ✓ | ✓ | ✓ | |||
| Surface preparation prior to powder coatings | ✓ | ✓ | ✓ | |||
| Stainless steel blasting and weld cleaning | ✓ | ✓ | ✓ | |||
| Blasting of aluminum, bronze, brass and zamak | ✓ | ✓ | ✓ | |||
| Blasting of titanium and special alloys | ✓ | ✓ | ✓ | |||
| Removal of heat treatment salts | ✓ | ✓ | ✓ | ✓ | ||
| Blasting of medical implants and prostheses | ✓ | ✓ | ✓ | |||
| Surgical instruments and medical sectors | ✓ | ✓ | ✓ | |||
| Pharmaceutical, food and electronics industries | ✓ | ✓ | ✓ | |||
| Decorative matte finish on stainless and aluminum | ✓ | ✓ | ✓ | ✓ | ||
| Engraving and matte finishing of glass, marble and granite | ✓ | ✓ | ✓ | |||
| Defect correction and part pretreatment | ✓ | ✓ | ✓ | |||
| Controlled surface roughness increase | ✓ | ✓ | ✓ | ✓ | ✓ |
RESOURCES AND RELATED LINKS
Technical data sheet, alternative abrasives and technical reports
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