Choose the abrasive by the profile the coating requires, the substrate, whether it can be recycled and the dust that can be tolerated: angular steel grit for shops and systems with recovery, garnet for clean, low-dust field blasting, slag for single-use work on large areas, aluminum oxide for stainless steel and non-ferrous metals, crushed glass as a metal-free option. Silica sand is excluded because of crystalline silica.
Abrasive is often chosen by habit or by price per tonne. Yet it determines the surface profile, the production rate, the amount of dust and waste, and sometimes the contamination left on the steel. This guide helps maintenance managers and project managers in Quebec and Ontario understand what the abrasive changes in the result. It complements our abrasive blasting page.
Why does the abrasive matter so much?
The abrasive matters because it creates the profile the coating anchors to, and because it can leave contaminants behind. The same cleanliness grade can be reached with several abrasives, but not with the same profile, the same dust or the same overall cost.
Four characteristics decide:
- Shape. An angular particle creates a profile; a round particle cleans and peens without cutting.
- Hardness and density. They set the blasting rate and the profile depth.
- Size. A coarser particle gives a deeper profile, a finer particle better coverage.
- Cleanliness. The abrasive must not bring salts, oil or dust onto the surface. Abrasive conductivity is checked per ASTM D4940.
The required surface profile is stated in the primer data sheet; it is measured per ASTM D4417 or ISO 8503.
How do the main abrasives compare?
Each abrasive has its range of use. The table below summarizes generally recognized trends; the project specification and the product sheets decide.
| Abrasive | Shape | Recycling | Dust | Typical use | Limits |
|---|---|---|---|---|---|
| Angular steel grit | Angular | Yes, in a closed loop | Low | Shop, blast room, vacuum recovery | Needs a recovery system, avoid on stainless |
| Steel shot | Round | Yes | Low | Cleaning, peening | Does not create an anchor profile |
| Garnet | Angular | Partial, depending on the loop | Low to moderate | Field work, tanks, structures | Higher initial cost than slag |
| Slag | Angular | Generally no | Moderate to high | Large field surfaces | Waste volume, composition to check |
| Aluminum oxide | Angular | Yes | Low to moderate | Stainless, aluminum, non-ferrous metals | Cost, equipment wear |
| Crushed glass | Angular | Generally no | Moderate | Metal-free option, some substrates | Particle breaks down quickly |
| Glass beads | Round | Partial | Low | Fine cleaning, finishing | Does not create an anchor profile |
Mineral and slag abrasives are covered by SSPC-AB 1, ferrous metallic abrasives by SSPC-AB 3, and the cleanliness of recycled steel abrasive by SSPC-AB 2. On the ISO side, the ISO 11124 series covers metallic abrasives and the ISO 11126 series non-metallic abrasives.
When to choose steel grit?
Choose steel grit when the abrasive can be recovered, cleaned and reused: in a blast room, a cabinet, or in the field with a vacuum recovery system. Its durability offsets its purchase cost only if it is recycled.
Angular grit creates the profile; round shot cleans but is not enough on its own for a coating that requires a profile. The two are sometimes mixed. Recycled grit has to stay clean: fines, dust and contaminants are removed in the loop, and SSPC-AB 2 sets the checks. On stainless steel, steel grit should be avoided because it leaves iron particles that rust on the surface.
When are garnet or slag preferable?
Garnet is preferable in the field when you want efficient blasting with little dust, and slag when you treat large surfaces on a single-use basis and the dust can be contained. Both are angular and create a good profile.
- Garnet. A dense, hard, low-friability particle that produces less dust and often gives the operator better visibility. It can be partly recycled with suitable equipment.
- Slag. Crushed industrial by-products, inexpensive to buy. They break down more, which increases dust and the volume of waste to manage. Some slags may contain trace metals: the safety data sheet and, if needed, an analysis will say.
To compare the two, the real cost includes the abrasive, consumption, containment and waste disposal, as explained in our article on sandblasting cost.
When to use aluminum oxide or glass?
Aluminum oxide is used on stainless steel, aluminum and non-ferrous metals because it leaves no iron on the surface. Crushed glass is a metal-free option for some substrates and jobs, and glass beads are used for fine cleaning without profile.
Aluminum oxide is very hard and recycles well in a closed loop. It also suits brush-off blasting of galvanized or stainless steel per SSPC-SP 16. Crushed glass breaks down quickly and is generally used once. For delicate parts or surfaces that need cleaning without altering the substrate, our glass bead and dry ice blasting page presents the options.
Why never use silica sand?
Silica sand is not used because its impact on steel releases respirable crystalline silica, which causes silicosis and other serious diseases. In Quebec, the Regulation respecting occupational health and safety (RSST) governs exposure to crystalline silica, and in Ontario it is one of the designated substances under Ontario Regulation 490/09.
Replacing it does not settle the dust question. The existing coating may contain lead or other metals, and every abrasive produces dust during blasting. So you need to:
- Check the safety data sheet of the abrasive for free silica and metal content.
- Protect operators with supplied-air respirators and exposure monitoring.
- Contain and ventilate the area to the level set in the specification, especially in an operating plant.
Our article on blasting in operating plants and dust control details the measures. When dust has to be kept to a minimum, wet blasting is another option.
How does the abrasive affect the profile and the coating?
The abrasive sets the depth and peak density of the profile, and therefore how the coating anchors. Too shallow a profile reduces adhesion; too deep a profile leaves peaks that pierce a thin film and promote rust.
Profile is adjusted by abrasive size, shape and hardness, blast pressure and nozzle distance. It is measured at the start of the job, then at regular intervals, because a recycled abrasive that wears changes the profile. Cleanliness grade is a separate requirement, explained in our NACE 2 / SSPC-SP 10 surface preparation guide. After blasting, bare steel has to be coated before flash rust appears.
How to get a suitable quote?
You get a suitable quote by describing the substrate, the planned coating, the required profile, the area to treat and the dust and waste constraints. These details allow the right abrasive and recovery method to be proposed.
Blasting is only one step of the protective coatings system: it is chosen together with the primer. Our crews and qualified subcontractors work from LaSalle, including the Côte-Nord and Saguenay-Lac-Saint-Jean. Send photos, dimensions and the coating data sheet through the request a quote form: pricing on consultation, reply within 24 business hours.
Frequently asked questions
Which abrasive gives the best profile?
An angular, hard abrasive sized for the required profile: angular steel grit, garnet, slag or aluminum oxide. Round particles clean without creating an anchor profile.
Can abrasive be reused in the field?
Yes for steel grit, aluminum oxide and, in part, garnet, with a recovery and cleaning system. Slag and crushed glass are generally used once.
Which abrasive for stainless steel?
An iron-free abrasive, such as aluminum oxide or clean garnet. Steel grit leaves iron particles that rust on stainless.
Can the abrasive contaminate the surface?
Yes. Dirty abrasive, or abrasive recycled without control, can bring salts, oil or dust. Conductivity per ASTM D4940 and the SSPC-AB 2 checks limit that risk.
Hicham M, P Eng, PMP
Engineer and project manager (PMP) at Induscoat. Over 16 years of experience in industrial coatings, composite repairs and wear protection on mining, energy and petrochemical sites in Canada and internationally.