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What is the shot blasting process?

Shot blasting is an aggressive pre-treatment process that involves propelling small abrasive particles at metal surfaces.

This prepares the surfaces for coatings or overlays. It is a process that many industries use, including:

  • Automotive
  • Aerospace
  • Construction
  • Foundry and steel
  • Rail
  • Shipbuilding

Shot blasting is also known as grit blasting.

Once you have carried out this pre-treatment, it makes it much easier to coat metal objects more effectively, ensuring that the coating you apply adheres effectively to the metal surface.

It is also a useful method for removing old coatings in preparation for applying fresh ones.

How the Shot Blasting Process Works

There are two ways to apply abrasive cleaning media to a surface. One is with compressed air, the other involves a centrifugal turbine.

The compressed air or pneumatic method is generally used in sandblasting and is a gentler abrasive blasting method.

Shot blasting tends to involve the mechanically-powered centrifugal process.

This uses a central wheel to accelerate the shot at its target. It enables the operator to direct the shot in specific directions, and at controlled speeds and quantities.

This might sound highly aggressive and even crude, but in fact you can achieve different types of surface preparation depending on the size and type of shot material you propel.

There are various materials you can use for this purpose, including:

  • Steel shot
  • Steel grit
  • Chilled iron grit
  • Copper shots
  • Aluminium pellets

Why is Surface Preparation Important?

When it comes to treating steel or other metal substrates, surface preparation is a crucial starting point.

If, for example, you want to protect a steel substrate from corrosion by adding a coating, you must first make sure the surface is in the right kind of condition that will enable the coating to adhere to it.

Surfaces can have layers of oil, dirt and dust, which you should clean before abrasive blasting.

But, typically, steel will also have mill scale, which forms on steel surfaces. Shot blasting will remove this.

This form of pre-treatment will clean the steel but also prepare it for coating.

Depending on the kind of finish your metal surface requires, different types of shot will give different surface preparations.

Smaller steel shots will provide a more polished finish, while larger ones will leave a coarser surface.

But regardless of the surface texture, shot blasting will ensure that it is uniform and therefore optimised for coating.

Shot Blasting Applications

Shot blasting is not simply a crude method of cleaning surfaces and removing stubborn debris.

It has a variety of applications, which cover:

  • Preparing surfaces and removing coatings
  • Creating a uniform surface
  • Etching
  • Removal of scale, dust, oxidation, burrs, flash rust and welding burns
  • Blending in tool marks or surface scratches.

What is Shot Peening?

Shot peening uses the same basic process as shot blasting, but with a different purpose.

Peening involves working a metal’s surface to strengthen it and improve its material properties.

The principle behind this is that you can strengthen the surface of metal by applying stress to it. The traditional way of doing this is by using a ball-peen hammer to expand the surface of the metal. This creates a compressive stress layer, which relieves the overall tensile stress.

In the shot peening process, each shot the acts like an individual ball-peen hammer blow. It uses the plasticity of the metal to prolong the life of the surface.

Peening makes the metal surface more resistant to fatigue, corrosion and cracking. It can also add a textured finish to the metal.

It is normal to apply both shot blasting and shot peening to metal parts as part of the manufacturing process.

When Should You Use Shot Blasting?

Using shot blasting will depend on the type of project you are working on, and what your desired end-result is.

Generally, shot blasting is suitable for coarser, more abrasive preparation of metal surfaces, involving dense materials and large-scale projects.

It is a highly aggressive process, and therefore not suitable for more delicate or smaller objects or parts.

But for preparing steel and other metal surfaces for coatings, or for peening them to strengthen them, it is the ideal answer. 

Find Out More

Is shot blasting right for your project? We specialise in a whole range of pre-treatments.

For more information or advice about shot blasting and our other services, please contact us.


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What is the shot blasting process?

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