Grit Blasting

Definition - What does Grit Blasting mean?

Grit blasting is a process where abrasive particles are accelerated and forcefully directed against a surface. These high-speed abrasive particles remove contaminants from the material's surface and condition the surface for subsequent finishing.

The impact of the grit on the metal surface puts the surface layer into compression, and this effect can be beneficial, for example, in reducing stress corrosion cracking in aluminum alloys.

Corrosionpedia explains Grit Blasting

Grit blasting as a technique of abrasive cleaning or surface preparation using sharp particles. In this technique, the surface in question is impacted at high velocity by hard, angular particles to such extent that unwanted material on the surface is removed, and a clean, active metal surface is exposed. It covers such processes as removal of scale, corrosion, paint and other surface films.

Grit is an abrasive material. Particles used in this process include:

  • Walnut shells
  • Various sands
  • Silicon carbide
  • Alumina
  • Emery particles

Methods of propelling the particles include:

  • Compressed air
  • Liquid streams
  • Vapor streams
  • Mechanical projection methods

Grit blasting performs several functions simultaneously. It removes mill-scale, rust, old paint and other contaminants, although oil and grease should be removed before blast cleaning. It is also used to remove sand and scale in the fettling of castings, and for dressing of stampings and billets, etc. It is often used to prepare surfaces before welding (removal of scale, rust or paint), and afterward to improve the adhesion of coatings (such as paint, or galvanizing). None of the shot blast, bead blast or sand blast processes produces a surface suitable for the subsequent application of a coating like grit blasting. Even bright steel will have a layer of iron oxide on the surface in welded areas, and coatings do not adhere to the oxide produced on flame or laser-cut edges.

Grit blasting will increase the surface area by producing a surface covered with small peaks and troughs. Due to the peaks being repeatedly hit by the grit, the surface is covered with small hooks where peaks have been bent over. Therefore, wire brushing, sanding or chemical treatment do not have the same effect as grit blasting.

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