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How to choose a suitable shotblasting abrasive?

There are many abrasives used for blast cleaning. A guide to the most popular abrasive media types and classifications is listed.

Classification : Reusable or Expendable Shotblasting Abrasives

Recyclable Abrasives :

Reusable shot blasting abrasives tend to be higher in cost than expendable abrasives. Reusable blast media is generally used in indoor 'closed circuit' environments such as shot blast chambers or blast cabinets, were the media can be recovered and re-used.  Examples of reusable abrasives are

Chilled Iron (http://www.sfeg.co.uk/abrasives-and-spares/abrasive-media/reusable-abrasives/chilled-iron-abrasive)

Aluminium oxide (http://www.sfeg.co.uk/abrasives-and-spares/abrasive-media/reusable-abrasives/aluminium-oxide-abrasive) ,

and glass bead (http://www.sfeg.co.uk/abrasives-and-spares/abrasive-media/reusable-abrasives/glass-bead). 

 

Expendable Abrasives -

Expendable abrasives, are designed to be used once only - as they break up on impact with the substrate.  They are typically used for open blasting / site work in outside environments where the blast media is not recovered.  These types of blast media tend to be low in cost.

Examples of this type include

J Blast Copper Slag (http://www.sfeg.co.uk/abrasives-and-spares/abrasive-media/expendable-abrasives/j-blast-abrasive),

Abrablast Medium (http://www.sfeg.co.uk/abrasives-and-spares/abrasive-media/expendable-abrasives/abrablast-abrasive) and Abrablast Fine

and Stonegrit (http://www.sfeg.co.uk/abrasives-and-spares/abrasive-media/expendable-abrasives/stonegrit-abrasive)

Garnet Blast Media (http://www.sfeg.co.uk/abrasives-and-spares/abrasive-media/expendable-abrasives/garnet-abrasive) falls between expendable and reusable. It can be used on site as an expendable, or is suitable for recycling in units such as blast rooms. It breaks down more quickly than aluminium oxide or chilled iron when recycled, but can normally be reused 5 – 10 times.

 

Classification : Blasting Media Particle Size

Abrasives are available in a range of particle sizes – normally stated in Micron, mm, or Mesh.

Expendable Abrasives - are sold in a broad size range, such as 0.2 – 0.7 mm, or 0.2 – 1.5 mm as the accuracy of the mix is not precise.

Reusable Blasting Abrasives are supplied in a narrower, more accurate, size range, such as G12 Chilled iron grit 0.3 – 0.71 mm , G24 chilled iron grit 0.6 – 1.0 mm, as they are accurately sieved and graded. 

All other factors being equal, the bigger the blasting media particle size, the greater anchor profile it will make.

An efficient abrasive selection is the finest abrasive that will remove the coating and give the required surface characteristic or profile. A fine abrasive will give you more impacts per volume. The more particles in the stream, the more work is accomplished in the same time. If the abrasive is too fine, the require depth profile will not be achieved which can lead to defects in the applied coating.

 

Classification  - Shape

The shape of the article effects how deeply it cuts into the coating and underlying substrate. Shapes are classified according to angularity.

Angular particles such as Chilled Iron Blast Media, J Blast Copper Slag, and Abrablast cut through coatings and rust, which gives fast cleaning rates, and sharp anchor patterns. Rounded particles such as Glass Bead and Steel Ball Shot produce an even, peened surface, which is excellent for breaking away hard brittle coatings and mill scale.

 

Classification  - Metallic or non- metallic abrasives

Shotblasting abrasives can be classified as metallic or non metallic.

Metallic abrasives

Metallic abrasives can withstand repeated impact and so are normally used as recyclable abrasives. They are often selected for cleaning applications where recovery and reuse of the abrasive is possible. The most widely used ferrous abrasives are the cast type such as Chilled Iron, and Steel Shot.

Non – Metallic Abrasives

Non- Metallic abrasives include aluminium oxide, glass beads, garnet, and natural and synthetic materials.

 

Classification  - Hardness

Generally speaking, the harder the particle, the deeper the profile it will impart.  This harness of a material can be measured on the MOHS scale. Softer abrasives, like plastic, and glass bead abrasive are good for removing dirt, oil, grease and paint without creating an anchor pattern in the underlying substrate.  Harder abrasives such as garnet abrasive and chilled iron grit will produce a greater surface profile.

 

Classification  - Density

Dense particles impact with more kinetic energy over a smaller surface area, resulting in a deeper profile. Dense particles also deform less, absorbing less energy upon impact. Examples of dense abrasives are chilled iron, and steel shot.

 

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Hogg North East & UK
0191 415 3030

Abraclean North West & UK
0161 480 8087

Complete Finishing Systems
01902 601 312

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