Why garnet is used
Garnet combines several properties that suit coating preparation in the field. Its hardness and density give efficient cutting and a sharp profile. Its particles break down more slowly than many slag abrasives, which reduces dust at the nozzle and improves visibility for the blaster. It also contains little crystalline silica, which is why it is often chosen where silica sand is restricted or prohibited. The actual composition, hardness and contamination levels vary by source, so the supplier's data and test reports should be reviewed for each lot.
Garnet compared with other abrasives
| Abrasive | Shape | Recycling | Typical use |
|---|---|---|---|
| Garnet | Angular to sub-angular | Limited, with suitable cleaning equipment | Open field blasting, tanks, structures |
| Coal or copper slag | Angular | Usually expendable | Large field projects |
| Steel grit | Angular | Many cycles in closed systems | Blast rooms, wheel blast, recovery systems |
| Glass bead | Round | Limited | Cleaning and finishing, not profile cutting |
The right choice depends on the profile and cleanliness required, containment, waste disposal, recycling equipment and the type of contaminant on the surface.
Quality requirements
- SSPC-AB 1 sets requirements for mineral and slag abrasives, including classes, cleanliness, water-soluble contaminants and crystalline silica content.
- ISO 11126-10 specifies almandine garnet for blast cleaning, and ISO 11127 gives the test methods for non-metallic abrasives.
- Abrasive should be dry, free of oil and low in soluble salts, since contamination carried by the abrasive ends up on the steel.
Limits and safety
Garnet is not dust-free. Blasting still generates dust from the abrasive and from the coatings being removed, which can contain lead, chromates or other hazardous materials. Respiratory protection, containment and air monitoring remain required, as defined by the applicable health and safety regulation and the project plan. Spent garnet mixed with old paint may also be classed as hazardous waste depending on test results.
Testing and disposal routes for spent abrasive should be planned before the project starts, since they affect both cost and schedule.
The abrasive is selected to reach the grade and surface profile on the coating data sheet, verified per ASTM D4417. See our abrasive blasting service.