Alumina Suspension
Comparable to Buehler MicroPolish / MicroPolish II, Struers alumina suspension, and Allied High Tech alumina suspension for the same final polishing step — at 20 to 40 percent lower cost.
Overview
Alumina Suspension
What This Product Is
Alumina suspension is a water-based suspension of deagglomerated aluminum oxide (Al₂O₃) particles used for intermediate and final polishing in metallographic preparation. Unlike colloidal silica, which polishes chemo-mechanically, alumina is a purely mechanical abrasive: the hard oxide particles cut the surface directly, making it a predictable, general-purpose oxide polish.
It is supplied in graded particle sizes — commonly 1.0 µm and 0.3 µm alpha alumina for polishing, and 0.05 µm gamma alumina for the finest final step. Deagglomeration keeps the particles dispersed so they polish cleanly rather than dragging as clumps.
Intended Use in Metallography
Alumina suspension is used for the final and near-final polishing steps, after diamond polishing. It is commonly selected when:
- A durable, purely mechanical oxide polish is wanted rather than a chemo-mechanical one
- Good edge retention is important
- Finishing general metals and alloys where colloidal silica is not required
- Stepping down through oxide sizes (1.0 → 0.3 → 0.05 µm) for a progressively finer finish
Typical Applications
Commonly used when finishing:
- General ferrous and non-ferrous metals and alloys
- Softer metals where a controlled mechanical polish is preferred
- Samples requiring strong edge retention
- Routine production and teaching-lab final polishing
Beyond metallography, alumina suspension is also used in:
- Petrography and geological thin-section finishing
- Optics and lens polishing
- Ceramics and advanced-materials preparation
- General precision polishing and lapping
Results depend on alumina grade, cloth selection, load, and rinsing between steps.
When This Product Is NOT Ideal
Alumina suspension may not be the best choice when:
- A deformation-free surface is required for EBSD or the most sensitive examination — colloidal silica is usually the better final step there
- The material reacts poorly to alumina or requires an oxide-free final polish
- Coarse material removal is needed, which belongs to a diamond or grinding step
Where This Fits in the Preparation Process
Alumina suspension is typically used:
- After fine diamond polishing
- As an intermediate-to-final oxide step, sometimes ahead of a colloidal-silica finish
Run on a soft, napless synthetic cloth. Keep the suspension shaken and dispersed, and rinse the sample and cloth before the alumina can dry.
Best-Practice Notes
- Shake before and during use to keep particles dispersed
- Do not let alumina dry on the specimen or cloth; rinse promptly
- Use a dedicated cloth per alumina size to avoid coarse-particle carryover
- Progress through sizes rather than jumping straight to the finest grade
Specifications
| Abrasive type | Aluminum oxide (alpha and gamma alumina) |
| Particle sizes | Typically 1.0 µm and 0.3 µm (alpha), 0.05 µm (gamma) — see product options |
| Action | Purely mechanical |
| Formulation | Deagglomerated, water-based suspension |
| Application | Intermediate and final metallographic polishing |
| Use | Manual and automated polishing systems |
| Micron Size | 0.05, 0.3, 1, 3 |
| Size | 8 oz, 16 oz, 32 oz, 1 Gallon |
| Custom sizing | Custom sizes and concentrations are made to spec if what you need is not listed |
| Compatibility | Buehler, Struers, LECO, Allied, and PACE — and all other major brands. |
Compatibility and Equivalents
Formulated for the same final polishing step as these brand products:
Runs on Buehler, Struers, LECO, Allied, and PACE systems — and all other major brands — with no change to your process. It is a comparable product for the same step — not a branded or drop-in item.
Same grading and micron sizing, typically 20 to 40 percent lower in price.
Request a free sample and test it on your own bench.
Named brand products are referenced only to identify the comparable item and prep step. We do not claim our product is identical to, or a replacement for, any trademarked product, and no affiliation or endorsement is implied.
Frequently Asked Questions
Alumina or colloidal silica for final polishing?
Alumina is a mechanical abrasive with good edge retention and predictable behavior; colloidal silica is chemo-mechanical and generally gives a more deformation-free surface for EBSD and difficult materials. Many labs use alumina for routine work and colloidal silica when the application demands it.
What is the difference between alpha and gamma alumina?
Alpha alumina (typically 1.0 and 0.3 µm) is harder and used for polishing steps; gamma alumina (0.05 µm) is finer and used for the final step. Stepping from alpha to gamma progressively refines the surface.
Why does the suspension need to be deagglomerated?
Alumina particles tend to clump. Deagglomerated suspensions keep them dispersed so they cut cleanly and do not drag agglomerates that cause scratching.
Can alumina suspension be used on automated polishers?
Yes, on both manual and automated systems. A water rinse near the end of the cycle helps clear residue before it dries.
Can alumina suspension be used outside metallography?
Yes. Alumina is a general-purpose mechanical polishing abrasive used well beyond metallography — in petrography and geological thin-section work, optics and lens finishing, ceramics and advanced materials, and general precision polishing. The same graded sizes apply; match the grade to the finish your application needs.