Sandblasting is the process of forcibly propelling a stream of sand (or other abrasive material) through a nozzle against a metal surface under high pressure in order to remove completely or partially the surface contaminants, enabling as well to roughen the surface for better coating adhesion.
Grit-blasting has been in wide use for several decades as the most effective method for preparing large metallic surfaces. The main advantages that led to its spread are that:
- Creates surface of high purity, free from paint and oxidation products.
- Provides high cleaning performance.
- Achieves proper surface for the subsequent application of the coating.
- Provides flexibility and adaptability to different applications or locations.
The three degrees of surface preparation by sand-blasting (cleaning qualities) are as follows:
Light grit blasting (simple cleaning), until the removal of loose mill scale, loose rust and detached impurities (adhered residues still remain).
Thorough grit-blasting (commercial grit-blasting) until all mill scale, rust and impurities are removed. In this case clean, dry compressed air or brush is used until 65% of surface is free from visible residue. The surface should be grey after the application of this method.
SA 2 ½
Very thorough grit-blasting. Mill scale, rust and impurities are removed so well (up to 95%) that the remaining traces look like light shades or lines.