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Whats The Best Grit Abrasives? Here's A Quick Guide

Updated: Jun 24, 2020

Abrasive blasting is a technique used to treat surfaces - It’s widely used in various industrial applications to clean, strengthen and protect equipment or machinery that are prone to the effects of rust and chemicals that would be used on a worksite. It involves the firing of abrasive particles through a nozzle using compressed air, which is extremely effective, but what kind of abrasive grit should you use? and What grit is the best to use?

In this article, we’ll be breaking down the different types of grit and how to use them to get the best result out of abrasive blasting.

The Different Uses of Abrasive Grit Blasting

Grit blasting has a wide range of uses in the industry, which include:

· Removing scale and fettling sand castings,

· Dressing billets and stampings,

· Preparing surfaces before welding and enhancing the adhesion of coating afterwards,

· Reducing the stress that may result in corrosion cracking for aluminium alloys,

· Clearing mould flashes on plastic components, and

· Providing a matte cosmetic finish on the surface of consumer products.

If you want to get an in-depth understanding of the size of the grit and grade you might need, here's a cool grit guide to assist you with figuring out the best size.

What type of grit is best for each surface?

Different surfaces require specific grit abrasives for cleaning and preparing them for painting. Abrasive grit blasting gives surfaces a better look.

1. Aluminium Oxide

Aluminium oxide is known for its superior strength and hardness. It is used as a raw material for different refractories, blasting abrasive, and anti-slip surfaces. It is designed for abrasive blasting, and it blasts using pressure on various surfaces like steel, marble, granite, and glass. Aluminium oxide can etch deeply, which makes it perfect for preparing surfaces before coating or painting.

2. Steel Shot

Steel is cost-effective and an excellent abrasive due to its high recyclability and toughness. This abrasive grit is suitable for removing contaminants from various surfaces effectively. It helps in texturing a surface to enhance its adherence for final coating or peening applications. The correct shape, hardness, and size play a vital role in the proper selection of media.

3. Walnut Shells

Crushed walnut shells are naturally-occurring abrasives. They’re the hardest of all available soft abrasives. Walnut shells come in a range of sizes to help in polishing and cleaning of smooth surfaces that incur damage from those harsher abrasives. Walnut shells are great for polishing soft stone, plastic, wood, fibreglass, and metals. You can use them for cleaning jewellery and gems in tumbling activities.

4. Plastics

Plastic abrasives are dry cleaning thermoset media made from crushed acrylic, polyester, or urea. They vary in terms of particle size and hardness. This is the best-regarded media for cleaning mould or plastic parts. It's common in industries such as electronics, boating, aviation, and automotive.

5. Silicon Carbide

Silicon carbide is one of the hardest abrasive blasting media available. This attribute makes it a perfect choice for the most challenging surface that requires finishing applications. It comes in different purities and colours. Its uses range from glass etching, polishing, lapping, and bonded abrasives.

6. Glass Beads

Glass may not be as aggressive as other blasting media such as silicon carbide or steel shot, but it's the best choice for applications that require a bright and smooth finish. Besides, glass beads are recyclable as many times as possible. They are highly used in blasting cabinets during finishing, peening, polishing, honing, and removing burrs.

5 Surfaces that’s best for Abrasive Blasting

1. Soft surfaces

Soft surfaces require a gentle type of abrasive blasting with lesser pressure exertion. Some of these smooth surfaces include glass, plastic, and chrome. Soda blasting uses sodium bicarbonate for blasting on the soft surface through air pressure.

2. Surfaces that require removal of fast cutting and smooth finish

The peening of a metal strengthens it but requires hard abrasives. Steel blasting abrasives are useful in smoothing surfaces and removing rust or paint from steel surfaces. Walnut shells, silicon carbide, and aluminium are also used to blast these surfaces.

3. Surfaces with high debris creepage

Surfaces with a high creeping of debris should be cleaned to minimise it. Vacuum blasting is the best choice that helps in removing any propelled surface contaminants and abrasives. The blasting material consists of a vacuum suction that sucks back all the stuff into a control unit.

4. Wood surface

A wooden surface requires a gentle, non-destructive technique to remove paint layers. Wood has a non-uniform hardness; hence, it requires adjustable pressures to preserve the soft grains. Whether modern or antique, the abrasive blasting applied must be gentler.

5. Aluminium surface

Walnut shells, sodium bicarbonate, or glass beads are often used as the abrasive material when blasting aluminium surfaces. Abrasives that are harder than aluminium should be avoided as they create a surface profile that could result in corrosion. Some of the harder abrasive media include steel grit and steel shot.

Final Thoughts

When abrasive blasting a surface, you should always ensure that the media is compatible; otherwise, it can cause significant damage to the surface. However, abrasive blasting enhances your machines’ appearance as well as life span.

An important note is that it’s crucial to apply the correct safety precautions, regardless of which grit you choose. Any small mistake could mean health hazards and potentially fatal injury if the right equipment isn’t used. You also need to ensure that you will need to adhere to the code of practice written by Safework Australia. That’s why it’s important to speak with qualified Abrasive Blasting specialists to provide you with the right advice.

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