5.4.2 Grit blasting of metals
Grit blasting is a mechanical surface treatment method for removing the uppermost layers of the substrate (e.g. rust) and exposing the actual base substrate. It causes compaction of the surface.
Grit blasting can be carried out on all metals with the exception of coated metals (galvanised or metals coated with other materials). In these cases the layer that has been applied could be damaged by grit blasting. Take care with very thin substrates!
- Prior to grit blasting the surface must always be thoroughly cleaned and degreased, to prevent “incorporation” of the contaminants into the surface and making them thereafter very difficult or impossible to remove.
- Optimum grit: Corundum with a grain size of 0.2 to 2 mm; Optimum blasting angle: 45°; Compressed air must be oil-free and dry
- After grit blasting remove all dust, etc. from the surface (e. g. using a disposable, white cloth soaked with cleaning agent or using compressed air)
Points to heed:
- Use suitable grit
- Use clean grit (replace contaminated grit straight away)
- Ensure the substrates are cleaned beforehand
- When blasting soft metals, there is a risk of some grit particles entering the metal (risk of corrosion)
- Remove all residues from the surface
- Use dry, oil-free compressed air
- Take care with thin substrates: Bending can occur due to the blasting pressure