Introduction to the shot blasting process

Shot blasting serves different purposes depending on the part and the desired result. Its main applications are:

• Sand removal and mill-scale removal on ferrous and non-ferrous castings and on forged parts.
• Mechanical descaling of wires, bars, plates and strip — an alternative to acid pickling, with no effluents and no hydrogen embrittlement.
• Shot peening, which induces compressive stresses on the surface and increases the fatigue resistance of springs, leaf springs and gears.
• Surface preparation prior to paint, anticorrosive coatings, rubber lining and other coatings.
• Shot blasting of concrete floors for coating application, and roughness restoration or rubber removal on airport runways.

In essence, shot blasting bombards the surface with abrasive particles at high speed. On impact, the abrasive strips off the adhered contaminants and leaves the surface clean and with the desired roughness. Impact speed, abrasive type and size, and projection angle determine the cleanliness grade and the anchor profile obtained.
Until the 1930s, shot blasting was done only with compressed air and nozzles. That method remains irreplaceable for certain jobs —such as the maintenance of already-erected structures— where the part cannot be brought to a machine.
Automatic shot blasting on production lines became possible only with the arrival of the centrifugal blast wheel. The blast wheel system is far more productive than compressed air and achieves a more uniform surface preparation. The choice between the two depends on the type of material, the size and shape of the parts, the condition of the surface to be cleaned and the required finish specification. In some cases other cleaning methods are combined before or after shot blasting to optimize the coating result.

A shot blasting machine is made up of six systems that work together. The correct operation of each one determines blasting quality, abrasive consumption and machine service life.

The type of equipment determines which abrasive can be used.
Compressed air equipment works with metallic or mineral abrasives alike (steel shot, aluminum oxide, glass beads, garnet, slag), allowing the most suitable one to be chosen for each job. Centrifugal blast wheel equipment, on the other hand, uses exclusively metallic steel abrasive —carbon or stainless— in various diameters depending on the desired finish.
In enclosed spaces and automatic processes, metallic abrasive offers clear advantages over single-use abrasives:

• Higher productivity and better work quality (uniform consistency, roughness and cleanliness).
• Lower abrasive cost per blasted area, since it is recycled hundreds of times.
• Lower consumption and less waste and dust generation.
• Lower investment in dust collectors and less environmental pollution.
• Better operator visibility and no health risks associated with silica.

Shot blasting is present across nearly the entire metalworking industry. It is used in foundry and forging, steelmaking and wire drawing, structural steel fabrication, the automotive and auto-parts industry, shipyards, oil & gas, agribusiness, mining, aviation and construction, among many other sectors.
Depending on the sector, the part, the goal and the most suitable equipment change: from mechanical descaling of wires and bars in steelmaking, sand removal of parts in foundries or gear and spring shot peening in automotive, to surface preparation of structures, tubes and cylinders prior to painting.

See the recommended equipment for each sector in detail on our Industries page.