Blasting consists of projecting an abrasive at high speed, by compressed air or by turbine, against a surface. The impact removes rust, scale, old paint or machining marks, and leaves a clean, slightly rough surface with a matt appearance. The word is generic: siliceous sand proper is rarely used today because of the health risks to operators, and corundum, glass beads, steel shot or gentler abrasives are preferred.
Sandblasting, bead blasting, shot blasting
- Sandblasting in the usual sense uses an angular abrasive, such as corundum, to strip or create a keying roughness.
- Bead blasting projects fine glass beads: the appearance is satin and uniform, with little material removal.
- Shot blasting uses metal shot; as shot peening, it is also intended to improve fatigue resistance.
Uses are many: preparing a part before powder coating or painting, obtaining an even matt base before anodising, evening out the appearance of a machined part, removing oxides from a welded plate fabrication. For preparation before painting, the ISO 8501-1 standard defines grades of cleanliness, including Sa 2½, which is very common. Note that the process removes a little material and changes the roughness; thin parts can distort, and threads, bores and precision bearing surfaces must be masked.
In a quote request
Specify the aim (stripping, keying, decorative appearance), the abrasive or appearance wanted (matt, satin), the grade of cleanliness or roughness targeted, the areas to protect and the next step in the process (painting, anodising). State the material and thickness of the parts: a thin sheet is not treated like a block. To choose the finish that follows, the guide anodising, powder coating and galvanising takes stock.