Shot Blasting
Shot blasting propels steel shot or grit at high speed onto parts to remove scale, rust, sand and old coatings, and to roughen surfaces for painting. It is the standard cleaning step for castings, forgings, fabrications and parts before coating.
What it is
Wheel-blast machines throw abrasive centrifugally onto parts tumbling in a barrel or passing on hangers or conveyors; air-blast rooms use nozzles for large or complex items. Steel shot gives a peened, cleaned surface; angular grit gives a sharper profile for coating adhesion.
The result is specified as a cleanliness grade (for example Sa 2½) and surface profile for coatings.
Typical applications
- Cleaning castings and forgings
- Descaling heat-treated parts
- Surface preparation before painting or galvanising
- Removing rust and old coatings
- Uniform matte finish on parts
Suitable materials
- Steel and cast iron
- Forgings and fabrications
- Stainless steel (with stainless or non-ferrous media)
- Aluminium (with suitable media)
Points to consider
- Mask threads, bores and machined faces that must not be blasted.
- Paint soon after blasting to avoid flash rust.
- Use non-ferrous media on stainless steel to avoid contamination.
- Thin parts can distort from aggressive blasting.
Frequently asked questions
What is the difference between shot blasting and sand blasting?
Shot blasting uses metallic shot or grit, often thrown by a wheel; sand or abrasive blasting uses mineral media from air nozzles. Both clean and prepare surfaces.
What does Sa 2½ mean?
A very thorough blast-cleaning grade under ISO 8501-1, the usual preparation for high-performance coatings.
Can machined parts be shot blasted?
Yes, with masking to protect threads, bores and precision faces.