Aluminum Oxide Grit Size Chart & Selection Guide
A complete engineering reference — FEPA and ANSI grit tables, anchor profile depths, substrate-specific recommendations, and a step-by-step selection framework for specification engineers and procurement professionals.
- Why Grit Size Is the Most Critical Specification
- FEPA vs ANSI: Understanding the Two Standards
- Master Grit Size Reference Chart
- Anchor Profile Depth by Grit Size
- 5-Step Grit Selection Framework
- Substrate-Specific Recommendations
- Grade & Grit Together: Brown vs White
- Blast Pressure, Nozzle & Grit Interaction
- Six Common Grit Selection Mistakes
- Frequently Asked Questions
1. Why Grit Size Is the Most Critical Specification
When engineers and procurement managers source aluminum oxide blast media, they routinely focus on price per kilogram and delivery lead time — and overlook the specification that most directly determines whether a blasted surface will perform as intended: grit size. Selecting the wrong grit produces outcomes at both extremes that are costly to correct.
Too coarse a grit creates an anchor profile that is deeper than the coating system is designed to bridge. The peaks of the profile can “tent” through thin topcoats, leaving unprotected metal exposed at the tips — a failure mode that accelerates corrosion directly under the coating and voids most manufacturer warranties. Too fine a grit, on the other hand, fails to generate adequate mechanical tooth for the coating to grip. The result is adhesion failure — delamination under service load, impact, or thermal cycling — often within months of application.
Grit size also directly governs the surface cleanliness grade achievable at a given blast pressure. Coarser grits physically remove more surface mass per impact event, enabling SSPC-SP 5 (White Metal) and SP 10 (Near-White) grades that finer grits cannot achieve efficiently. Finally, grit size determines media consumption rate — coarser particles carry more kinetic energy and fracture more readily on impact, increasing the top-up requirement per square meter treated.
This guide provides a comprehensive, engineering-grade reference for grit size selection across both brown fused and white fused aluminum oxide — the two grades manufactured and exported by 江苏恒利宏科技股份有限公司 For a full introduction to both product grades and all other aspects of aluminum oxide blast media, see our complete buyer’s guide: Aluminum Oxide Blast Media: The Complete Buyer’s Guide.
2. FEPA vs ANSI: Understanding the Two Standards
Aluminum oxide blast media is graded under two principal international grit size systems. Understanding which system your coating specification, equipment manual, or procurement document references prevents ordering errors that can set a project back by weeks.
FEPA (Federation of European Producers of Abrasives)
FEPA is the dominant global standard for loose abrasive grains used in blasting and abrasive applications. FEPA F-grits (for bonded and coated abrasives) are designated with the prefix “F” followed by a number — for example, F24, F36, F60. A higher FEPA number indicates a finer particle. FEPA specifies the allowable particle size distribution through a defined sieve stack analysis: the standard prescribes maximum percentages for the coarse fraction, the median fraction (D50 window), and the fine fraction, ensuring every manufacturer’s F36, for instance, falls within the same particle size envelope regardless of country of origin.
ANSI (American National Standards Institute)
ANSI B74.12 governs loose abrasive grains in the United States and Canada. ANSI grit numbers — often expressed as simple mesh numbers without a prefix (#36, #60, #120) — are broadly equivalent to FEPA F-grits of the same number, though there are subtle differences in the permissible size distribution tolerances at each grade. In practice, for blast media selection purposes, FEPA F36 and ANSI #36 are interchangeable; the particle size windows are closely matched.
| FEPA Designation | ANSI Equivalent | Governing Standard | Primary Market | Notes |
|---|---|---|---|---|
| F12–F220 | #12–#220 | FEPA 42-2:2006 | Europe, Asia, global export | Most widely used for blast media specification |
| F240–F1200 | — | FEPA 42-2:2006 (fine range) | Europe, Asia | Fine polishing range; ANSI P-grits differ significantly here |
| P-grits (P12–P2500) | — | FEPA 43-1:2006 | Coated abrasives (sandpaper) | Not used for blast media; different distribution tolerance |
3. Master Grit Size Reference Chart
The table below is the primary engineering reference for aluminum oxide blast media grit specifications. All particle size values reflect FEPA 42-2 D50 midpoints. Anchor profile depths are indicative values for angular fused aluminum oxide blasted at 70–80 PSI on mild steel at 25–30 cm standoff; actual results vary with blast pressure, nozzle wear, standoff distance, substrate hardness, and equipment design. The grade availability column indicates whether brown fused (B), white fused (W), or both (B+W) are commercially stocked by Henglihong at that grit.
| FEPA Grit | ANSI Mesh | D50 Particle Size | Particle Range (µm) | Anchor Profile Rz | Grade Available | Primary Use |
|---|---|---|---|---|---|---|
| F12 | #12 | ~2,000 µm | 1,700–2,360 | 100–130 µm | 棕色 | Heavy mill scale, large structural steel, civil infrastructure |
| F14 | #14 | ~1,700 µm | 1,400–2,000 | 95–125 µm | 棕色 | Heavy scale, bridge girders, ship hull pre-treatment |
| F16 | #16 | ~1,400 µm | 1,180–1,700 | 80–110 µm | 棕色 | Ship hulls, offshore platforms, heavy rust removal |
| F20 | #20 | ~1,000 µm | 850–1,180 | 70–95 µm | 棕色 | Heavy fabrication, structural steel coating prep |
| F24 | #24 | ~850 µm | 710–1,000 | 60–85 µm | Brown + White | General steel fabrication, pipe coating, tank linings |
| F30 | #30 | ~710 µm | 600-850 | 55–75 µm | Brown + White | Steel prep for high-build coatings, industrial machinery |
| F36 | #36 | ~600 µm | 500-710 | 40–65 µm | Brown + White | Near-white blast, moderate-build protective coatings — most popular blast grade |
| F40 | #40 | ~500 µm | 425-600 | 35–55 µm | Brown + White | General industrial coatings, automotive fabrication |
| F46 | #46 | ~425 µm | 355-500 | 30–50 µm | Brown + White | Powder coating prep, automotive, general fabrication |
| F54 | #54 | ~355 µm | 300-425 | 25–42 µm | Brown + White | Lighter steel prep, aluminum components, thin-film primer |
| F60 | #60 | ~300 µm | 250-355 | 22–36 µm | Brown + White | Precision cleaning, dental lab, thin epoxy coatings |
| F70 | #70 | ~250 µm | 212-300 | 18–30 µm | Brown + White | Fine steel prep, stainless steel surface conditioning |
| F80 | #80 | ~212 µm | 180-250 | 15–26 µm | Brown + White | Stainless steel, precision components, light cleaning |
| F90 | #90 | ~180 µm | 150-212 | 12–22 µm | 白色 | Precision metal prep, electronics substrate cleaning |
| F100 | #100 | ~150 µm | 125-180 | 10–18 µm | 白色 | Fine component prep, dental bonding surface treatment |
| F120 | #120 | ~125 µm | 106-150 | 8–16 µm | Brown + White | Glass etching, frosting, stainless descaling, medical implant prep |
| F150 | #150 | ~100 µm | 75–125 | 6–12 µm | 白色 | Fine glass work, ceramic prep, orthopedic implant surface texture |
| F180 | #180 | ~80 µm | 63-106 | 5–10 µm | 白色 | Precision ceramics, optics, fine glass etching |
| F220 | #220 | ~68 µm | 53-75 | 4–8 µm | 白色 | Ultra-fine glass, ceramics, electronic components, micro-blasting |
| F240–F1200 | — | 8–58 µm | Varies | <4 µm | 白色 | Lapping, polishing, optical and electronic component finishing |
4. Anchor Profile Depth by Grit Size
The anchor profile — also called surface roughness, surface profile, or blast profile — is the peak-to-valley height (Rz) of the micro-topography created by blasting. It is the mechanical key that allows protective coatings to grip the substrate surface. Profile depth is primarily governed by grit size, with secondary influence from blast pressure, nozzle angle, standoff distance, and substrate hardness.
The visual below shows the relative profile depth achievable across key grit sizes at standard blast conditions (70 PSI, mild steel, 25 cm standoff, angular fused aluminum oxide):
How to Measure Anchor Profile
Two methods are accepted by most international coating inspection standards:
- ISO 8503 / Testex Replica Tape (ASTM D4417 Method B): Press-O-Film or equivalent replica tape is pressed onto the blasted surface, creating a physical replica of the profile. The replica thickness is measured with a micrometer and the substrate thickness subtracted. Simple, portable, and produces a permanent record. Accepted by virtually all coating inspection protocols.
- Electronic Profilometer (ASTM D4417 Method C / ISO 4287): A contact stylus profilometer traverses the surface and computes Rz, Ra, and other roughness parameters. Provides more data than replica tape but requires equipment calibration and is sensitive to measurement direction relative to blast pattern.
Minimum measurement requirement: five independent readings per inspection area, with the mean reported against the coating manufacturer’s specified tolerance.
5. Five-Step Grit Selection Framework
Use this systematic process for any new blasting application. It takes approximately 15 minutes to complete with a coating product data sheet in hand — and prevents the far more expensive outcome of re-blasting after a specification non-conformance.
6. Substrate-Specific Grit Recommendations
Different substrates require different grit strategies. The table below consolidates recommended grit ranges, grade selection, and key considerations for the most common blast-media application scenarios.
| Substrate / Application | Recommended Grit | Grade | Target Profile (Rz) | Key Consideration |
|---|---|---|---|---|
| Structural carbon steel (SP 10) | F24–F36 | 棕色 | 50–85 µm | Most economical choice; high recyclability in closed systems |
| Structural carbon steel (SP 5) | F16–F24 | 棕色 | 70–110 µm | Higher pressure required; check substrate section thickness |
| Stainless steel (all grades) | F46–F80 | 白色 | 20–40 µm | White grade mandatory — iron from brown grade causes corrosion halos |
| Aluminum alloys | F60–F120 | 白色 | 10–25 µm | Use lower pressure (40–60 PSI); aluminum is soft and deforms under coarser grits |
| Titanium (aerospace) | F80–F120 | 白色 | 8–18 µm | AMS 2431 compliance required; no iron contamination acceptable |
| Cast iron | F24–F46 | 棕色 | 40–70 µm | Brittle substrate — excessive pressure risks micro-fracture at casting skin |
| Galvanized / zinc-coated steel | F46–F80 | Brown or White | 20–40 µm | Sweep blast only — coarser grits remove zinc and defeat the purpose |
| Glass (etching / frosting) | F120–F220 | 白色 | 6–16 µm | White grade avoids color contamination; reduce pressure to 20–35 PSI |
| Glass (deep artistic etch) | F60–F120 | 白色 | 15–30 µm | Coarser grit + resist stencil for relief / three-dimensional effects |
| Medical implants (Ti / Co-Cr) | F120–F220 | 白色 | 4–16 µm | Traceability and batch documentation required; ISO 9001 supplier minimum |
| Dental ceramic bonding | F80–F150 | 白色 | 6–18 µm | Micro-blast unit at 30–50 PSI; single-use media for cross-contamination prevention |
| Thermal spray (HVOF) prep | F24–F36 | 白色 | 50–80 µm | White grade prevents iron contamination of thermal spray bond coat |
| Anti-slip floor coating additive | F46–F80 | Brown or White | N/A (incorporated in coating) | Size selected for coating thickness; see our anti-slip guide |
| Stone / concrete texturing | F16–F36 | 棕色 | 60–100 µm | High nozzle pressure; use direct-pressure blast system for adequate impact energy |
7. Grade & Grit Together: Choosing Brown vs White
Grit size and product grade are two independent variables that must both be specified correctly. A common error is selecting the right grit but the wrong grade — for example, specifying F60 brown fused aluminum oxide for stainless steel prep, where the correct specification is F60 white fused. The selection logic is straightforward:
| Decision Criterion | Specify Brown Fused (BFAO) | Specify White Fused (WFAO) |
|---|---|---|
| Substrate material | Carbon steel, cast iron, concrete, stone | Stainless steel, aluminum, titanium, glass, ceramics |
| Iron contamination tolerance | Acceptable (substrate itself contains iron) | Zero tolerance — white grade required |
| Service environment | General industrial, atmospheric exposure | Immersion, food contact, medical, offshore, pharmaceutical |
| Governing specification | SSPC, ISO 8501, general industrial | AMS 2431, MIL-A-22262, EN ISO 11126-7, medical OEM spec |
| Budget priority | Cost-minimization — brown is 30–60% lower unit cost | Quality / compliance — white premium is justified |
For a comprehensive analysis of brown vs white aluminum oxide across 12 application scenarios, see our dedicated article: Brown vs White Aluminum Oxide: Which Should You Use?
8. Blast Pressure, Nozzle & Grit Interaction
Grit size determines the maximum achievable anchor profile — but blast pressure, nozzle bore diameter, and standoff distance determine how much of that potential is realized in practice. Understanding the interaction prevents both under-performance (profile too shallow) and over-blasting (profile exceeds specification, surface roughness damages thin sections or creates uncoatable peaks).
Pressure Effects on Profile Depth
For a given grit size, increasing nozzle pressure increases both impact energy per particle and profile depth — but with diminishing returns above approximately 90 PSI (6.2 bar) for most aluminum oxide grits. Beyond the “saturation” pressure for a given grit, additional pressure primarily increases media fracture rate, dust generation, and compressor energy consumption without meaningfully increasing profile depth. The practical operating envelope for most industrial blast work is 60–100 PSI (4.1–6.9 bar).
| Blast Pressure | Typical Application | Effect on F36 Profile (Rz) | Media Consumption Rate |
|---|---|---|---|
| 20–40 PSI (1.4–2.8 bar) | Glass, light metals, dental, precision | ~20–35 µm (under-driven for steel prep) | Low |
| 40–60 PSI (2.8–4.1 bar) | Aluminum, sweep-blast, light cleaning | ~28–42 µm | Low–Moderate |
| 60–80 PSI (4.1–5.5 bar) | General steel prep, fabrication shop standard | ~40–60 µm | Moderate |
| 80–100 PSI (5.5–6.9 bar) | Heavy descaling, SP 5 / SP 10 specification work | ~55–75 µm | Higher |
| >100 PSI (>6.9 bar) | Specialized heavy-duty only | Minimal additional gain; high media loss | High |
Nozzle Bore Size & Grit Compatibility
Nozzle bore diameter must be matched to grit size to prevent blockages and ensure consistent media flow. A general rule: the nozzle bore diameter should be at least four to five times the D90 particle size of the grit being used. For F36 (D90 ≈ 710 µm), a minimum 3 mm bore nozzle is required; for F12 (D90 ≈ 2,360 µm), an 8–10 mm bore is appropriate. Undersized nozzles cause irregular flow, pressure drop across the nozzle, and accelerated nozzle wear — all of which increase operating cost.
Standoff Distance
Increasing standoff distance reduces kinetic energy at impact and produces a shallower profile. For most blast media applications, a 20–30 cm standoff at perpendicular nozzle angle represents the optimal balance between profile depth and blast pattern coverage width. Angling the nozzle 10–15° off perpendicular is common for heavy mill scale removal — the oblique angle increases the shearing component of impact, which assists in undercutting and detaching tightly adherent scale.
9. Six Common Grit Selection Mistakes
Based on technical inquiries from industrial customers, the following specification errors account for the majority of blasting non-conformances reported to our application engineering team. Each one is preventable with the frameworks provided in this guide.
- Specifying grit without reading the coating data sheet. Choosing a “standard” grit based on habit or price rather than the topcoat manufacturer’s stated anchor profile requirement is the single most common root cause of adhesion failures. Always start with the PDS.
- Using brown fused aluminum oxide on stainless steel. Iron contamination from brown-grade media causes corrosion initiation on stainless, duplex, and austenitic alloys. Always use white fused aluminum oxide on iron-sensitive substrates. See: Brown vs White Aluminum Oxide.
- Selecting too coarse a grit for thin-section or thin-coat work. Applying F24 blast media to 2 mm aluminum sheet creates substrate distortion. Applying F24 to a substrate destined for a 60 µm primer creates a profile that exceeds the coating thickness, leaving unprotected steel peaks.
- Ignoring nozzle wear condition. A worn nozzle produces an irregular, enlarged blast pattern with reduced impact velocity — effectively behaving like a coarser but slower grit. Replace tungsten carbide nozzles when bore diameter has increased by 1–1.5 mm beyond nominal.
- Not classifying and reclaiming spent media correctly. Running spent media that has degraded below the minimum particle size produces an anchor profile shallower than specified — without any visual indication at the nozzle. Track profile depth measurements, not just media age, as the criterion for top-up. Our reusability guide covers this in detail: Is Aluminum Oxide Blast Media Reusable?
- Using a single grit blend where a graduated mix would outperform. For substrates with a combination of heavy corrosion and a tight upper profile limit, a 70/30 blend of F24 and F46 (for example) can simultaneously remove heavy contamination and moderate the peak profile height more effectively than either grit alone. Custom blends are available on request from Henglihong.
10. Frequently Asked Questions
The FEPA F-grit number is a nominal size designation that corresponds to a standardized particle size distribution — specifically, the combination of sieve screen openings through which the majority of the material passes. A higher FEPA number means a smaller (finer) particle size. FEPA does not specify a single exact particle size; it specifies the permissible percentages retained on a stack of calibrated sieves, defining the coarse end, the median D50 window, and the fine fraction. This distribution approach ensures consistent blasting performance across different manufacturers’ products with the same grit designation.
For most general industrial protective coating applications — epoxy, polyurethane, zinc-rich primers — F36 is the more versatile choice. It produces an anchor profile of 40–65 µm, which sits in the optimal zone for most 150–400 µm DFT coating systems. F46 is appropriate when the coating specification requires a shallower profile (30–50 µm), or when the substrate is lighter-section material where F36 creates unnecessary roughness. If you are targeting SSPC-SP 10 or SP 5 for heavy-duty immersion or offshore service, F36 is the standard first choice.
Yes, and this is sometimes done in practice. Blending, for example, 70% F36 and 30% F24 will shift the achieved profile toward the coarser end while maintaining more of the fine-particle cutting action of F36. However, blended grit systems are harder to reclaim cleanly in a media classifier because the two fractions separate over time as the smaller particles fracture and degrade faster. For most standard applications, selecting a single grit that spans your target range is simpler and more controllable. Contact our application engineering team if you need guidance on custom blend design.
Both Ra and Rz quantify surface roughness, but they measure different aspects of the profile. Ra (arithmetic mean roughness) is the average absolute deviation of the surface profile from the mean line — it smooths out peaks and valleys equally. Rz (maximum height of profile, averaged over five sampling lengths) is more sensitive to the extreme peaks and valleys that determine a coating’s ability to mechanically bond to the substrate and the risk of peak-tenting through thin coatings. For blast media specification and coating adhesion assessment, Rz is the preferred parameter — it is what ISO 8503, ASTM D4417, and most protective coating data sheets specify. Ra alone is insufficient for blast prep quality control.
Ambient conditions do not directly change the mechanical action of blasting, but they are critical to the quality of the prepared surface. Most coating specifications — including SSPC-SP 1 and ISO 8504-2 — require that blasting is not performed when: the steel surface temperature is less than 3 °C above the dew point; relative humidity exceeds 85%; or surface temperature is below 5 °C (conditions that prevent proper coating application even if the blast profile is correct). Blasting under these conditions produces a correctly profiled but immediately re-contaminated surface (flash rust forms within minutes), requiring re-blasting before coating. Always check dew-point conditions before commencing blast work outdoors.
A “mil profile” is the anchor profile depth expressed in thousandths of an inch (mils), a unit used primarily in North American coating specifications (SSPC, NACE, and US Navy specifications, for example). The conversion is straightforward: 1 mil = 25.4 µm. Therefore, a 2–3 mil profile specification is equivalent to 51–76 µm Rz — placing it squarely in the F24–F36 grit range for angular aluminum oxide at standard blast pressures. The FEPA grit-to-mil relationship is not rigid (pressure and nozzle condition shift it), but as a working approximation: F36 ≈ 1.5–2.5 mils; F24 ≈ 2.5–3.5 mils; F16 ≈ 3–4.5 mils.
Need Help Specifying the Right Grit?
Our application engineering team at Jiangsu Henglihong Technology can review your coating specification and substrate requirements, and recommend the optimal grit size and grade for your project — with sample quantities available for trial evaluation.
Related Resources
Continue building your aluminum oxide expertise with these guides from the Henglihong resource library:
- Aluminum Oxide Blast Media: The Complete Buyer’s Guide
- Brown vs White Aluminum Oxide: Which Should You Use?
- Aluminum Oxide vs Garnet Blast Media: Full Comparison
- How to Choose Aluminum Oxide Blast Media for Steel Surfaces
- Is Aluminum Oxide Blast Media Reusable? How Many Times?
- Aluminum Oxide Blast Media for Aerospace & Medical
- Aluminum Oxide for Glass Etching & Frosting
- Bulk Aluminum Oxide Blast Media – Wholesale Pricing & RFQ
- Aluminum Oxide Anti-Slip Additive for Floor Coatings
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