Sandblasting is an abrasive cleaning technique that removes rust, paint, scale or other contaminants from ferrous and non-ferrous surfaces, leaving a profile on the surface ready for industrial painting and protective coatings to be applied.
The abrasive media works similar to sandpaper except it is propelled with extreme force by compressed air, which makes it a fast and effective way to achieve a clean and profiled surface.
No matter what the type of surface you are preparing, sandblasting is the first step in any steel process.
How Sandblasting Works
Sandblasting is the process of propelling fine, abrasive materials at high velocities to achieve a number of results. There are varying types of machines and parts/accessories, so there is not really one way a blast machine works.
However, for the most part, they operate on this simplified notion:
User-Loaded Media + Pressurised Air = Blasting
The main components of a blast machine are:
- Blast pot or media reservoir.
- Nozzles accelerate the air/abrasive as the mixture exits the end of the blast hose.
- Inlet and outlet valves to monitor the inflow and outflow of air.
- Pop-up valve responds to pressure put into the system.
- Media valve regulates the abrasive flow from the blast pot.
- A blast machine also comprises a number of hoses.
Media is loaded into the machine and pressurised, hoses are connected and when the handle is engaged, a mixture of air and abrasive sprays through the nozzle to begin sandblasting.
Types of Sandblasting Abrasive Media
Sandblasting media is available in a variety of shapes and sizes, as well as hardness and density levels. While you may believe that sand is used commonly as the abrasive material of choice, there are actually many different materials that can be used.
The best type of abrasive media depends on the surface material and the purpose of the sandblasting. The most common media types are garnet, aluminium oxide, glass bead, plastic.
More recently, garnet is the choice for a variety of sandblasting purposes as it is usable for both surface preparation and finished results and the advantages have propelled it to take an ever-widening portion of the market.
Shape and Size
From angular to round, there is a sandblasting media shape and size for every abrasive blasting project.
Angular materials are the sharpest and include aluminium oxide. Sub-angular media, such as garnet, is slightly less sharp.
Sandblasting media is categorised according to grit size. For example, garnet ranges in size from coarse 20/40 and 30/60 grit to fine 80 and 120 grit.
Hardness and Density
The hardness and density of sandblasting particles determine the depth of penetration into the target surface – or how hard the abrasives clean the surface.
Hardness, however, does not necessarily equal strength.
Density, which measures the weight of the particles by volume, is another important characteristic of sandblasting media. A denser particle, such as steel shot, will penetrate more deeply than a less dense particle of the same size.
How to Choose Sandblasting Media
Some of the things you should consider when choosing an abrasive are hardness, density, shape of the abrasive, the type of profile the abrasive will leave, friability, how many times you can recycle the abrasive, and overall cost.
If garnet is your choice of media then consider the correct grit size to fit the purpose, for example 20/40 and 30/60 grit garnet are best suited for: heavy machinery, road marking removal, steel boats or general heavy stripping. Where 80 and 120 grit garnets are ideal for: automotive, lighter rust removal, graffiti removal, aluminium boats or whenever very fine media is needed.
When in doubt, start with a softer medium for your project and work up to harder media if needed. Kelmscott Blast & Paint tend to stick to Garnet for most sandblasting projects.
Hire Abrasive Blasting Professionals
With so many materials to choose from, it is wise to hire a sandblasting business to complete any abrasive blasting project for you.
Sandblasting companies are familiar with the latest products and can choose the best media for your job. Whether you are polishing granite or using abrasive sandblasting to strip paint from a boat, you can rely on the experienced team at Kelmscott Blast & Paint for the best sandblasting results.