What are the types of abrasive blasting media? This article looks at the various blast materials available and how they can benefit your blast cleaning requirements.
How To Choose The Right Abrasive Media?
Both grit blasting and shot blasting techniques fall under the process commonly known as abrasive blasting.
Many people will use any or all of these terms to refer to these processes, despite the various distinctions. Simplified, grit blasting entails using angular particles as an abrasive blasting media, while shot blasting uses smooth or rounded particles.
Types Of Abrasive Blasting
Abrasive blasting is also known as sandblasting, grit blasting or media blasting. While people often get the various names mixed up, each type of blasting comes with its own mediums, uses, advantages and disadvantages.
However, in the end, the main use of abrasive techniques is to clean or prepare a surface to be modified or painted.
Depending on what you want to do with the material's surface, different abrasive techniques will be more suited than others. There are three common elements to any abrasive work.
The first is that there will usually be a blasting cabinet or area where the work will occur. They will all propel their abrasive blasting media at the chosen surface in one way or another. Finally, it is the most efficient and sustainable way to prepare industrial metal surfaces.
WHATS THE DIFFERENCE BETWEEN SANDBLASTING AND SHOT BLASTING?
Here is a list of the different types of abrasive blasting, their blasting applications, and their positives and negatives.
Sandblasting is one of the most common and well known abrasive techniques. Using either free silica sand or quartz, this technique uses compressed air to fire a stream of the abrasive material at the chosen surface.
The main benefit of sandblasting is that it creates an even distribution of material, creating a smooth, satin finish.
Depending on the material you have, sandblasting may or may not be the best option. Sandblasting is commonly used to remove rust from metallic surfaces.
You should also be aware that silica sand is rarely used as an abrasive medium today. Silica sand forms toxic dust clouds when fired from a sandblaster, which can cause serious respiratory conditions.
Wet blasting seeks to solve the issue often found with air blasting in that it creates huge clouds of dust. In wet blasting techniques, water is injected into the equipment's nozzle to help mitigate this issue.
Some varieties of wet blasting even mix water with the abrasive blasting media before being projected onto the surface.
In either case, the mix of air, abrasive material and water is forced from the nozzle into the surface of the chosen material at high pressure to clean or prepare the surface.
This technique is best used to control the amount of medium sprayed during the process to limit dust clouds.
Vacuum blasting is another perfect way to reduce dust clouds during the abrasive process. The blasting equipment comes fitted with a vacuum that will gather any excess blast media as it is propelled from the nozzle.
This excess material is then repurposed back into the equipment to carry on the abrasive procedure.
Given that excess material is repurposed, vacuum blasting is one of the most cost-effective abrasive methods. Blasting mediums are fairly cheap, but repurposing it will make your money go much further.
However, this repurposing does mean that low-dust, wet blasting processes take a little longer than other methods.
Centrifugal blasting, otherwise known as wheel blasting, is a method of projecting the abrasive material using a bladed wheel. This wheel spins at high speed to blast the medium towards the chosen surface.
Compared to compressed air methods of propulsion, centrifugal blasting creates an even smoother surface than sandblasting.
However, there are some drawbacks. The main disadvantage to this abrasive blasting method is that larger equipment is required, meaning it is a far less portable option.
This method is best suited for surfaces that are already fairly smooth and require long-lasting abrasive blasting.
Soda blasting is the most recent innovation, using sodium bicarbonate or soda lime as an abrasive blasting media.
It propels this medium using compressed air and is especially good at removing certain contaminants from the surface of materials. It is also best suited to more delicate materials that could not stand up to harsher techniques.
Soda blasting removes contaminants because the medium shatters when it strikes the material's surface. This exerts more pressure than would otherwise be produced using other blasting methods.
Soda blasting is also far gentler on surfaces than other abrasive options, given that it requires far less pressure to create the same effect.
As the name might suggest, steel grit blasting uses steel shot as an abrasive medium. Naturally, this technique is best used on really strong materials, such as other metals.
This method is primarily used to create a very smooth finish to a material, cut it, shape it, or peen.
Aside from steel, materials such as aluminium oxide, silicon carbide and even walnut shells can be used as abrasive blast media.
The medium you choose should be determined by the type of material you are using the abrasive equipment on and the final finish you are attempting to create.
This is the only blasting technique that does not require a medium. Bristle blasting is essentially a steel-wire brush that is rotated against the chosen surface to clean it. If you have very corroded metals, bristle blasting is often the best option.
Dry-ice blasting is another new addition to the blasting family, which uses compressed air to fire carbon dioxide pellets at the chosen surface. This method is mostly used when cleaning food equipment, given that the medium is non-toxic and will not react with any contaminants.
The speed of the pellet striking the surface creates a thermal shock that breaks the bonds between it and the contaminant.
An additional benefit is that the pellets melt away once exposed to the warmer outside temperatures, meaning there is nothing to clean up once the blasting process is finished.
The pellets are environmentally friendly and cause no damage to the actual surface of the material you are blasting. This makes it perfect for blasting delicate materials.
Pencil blasting uses a fine powder with compressed air to create a narrow abrasive stream for very precise cleaning. You can also alter the pressure of the compressed air to provide a cutting, drilling or deburring stream.
Pencil blasting is so powerful and precise you can use it in diamond or glass etching. Ultimately, its primary use is for abrasive cleaning or preparation that requires a lot of precision.
The last type of abrasive blasting we'll look at is bead blasting. This method uses compressed air and glass beads to create a cleaning, peening and deburring stream.
The glass beads create micro dimples when they strike the material's surface, leading to a smoother, bright finish. The glass is also entirely recyclable, making it one of the most cost-effective blasting processes.
Blasting for Surface Preparation and Finishing
When preparing or finishing a surface, choosing the right abrasive blast media is crucial; different abrasive mediums will give different finishes, meaning depending on what you want to create, you need to be careful in what you choose.
The different surfaces created by abrasives will also allow coatings to bond in different ways, meaning you should also consider which coating you want to apply when choosing a medium.
Factors When Selecting An Abrasive
When choosing your abrasive blasting media, it is best to consider the Mohs hardness scale, which measures the hardness of different materials. For example, talcum powder would score a 1, while diamonds would score a 10. Essentially, the higher the number, the harder the material. This also means that higher numbered materials can etch or abrase lower numbered ones.
Lower-numbered materials come with the added benefit of creating a finer finish, while higher-numbered materials are best at removing contaminants or rust. If you want to avoid leaving an anchor pattern or remove other substances such as grease or oil, softer materials are often best.
Do you require blast cleaning in London or throughout the UK? Contact us on our phone number or via email for further information or advice. If you are interested in a dustless blasting service, RM Specialist Blast Cleaning is always happy to help and assist you.
We can offer high-quality training that may only take around 5 or so minutes. We have professionals on standby so that you can happily stop by and demo our machines at any hours of the day.