What Type of Sandblast Media to Use on Rust?by Heather BlissUpdated July 13, 2023
Sandblasting your automotive can remove rust stains and corrosion and help prepare your car for new paint. However, you must choose the sandblasting media carefully; the wrong sand blaster gun may damage the metal panels of your car, causing small dents or other flaws that will not result in good surface preparation. When sandblasting rust away, a good rule of thumb for the media is to start gently and step up the stripper with high pressure as you go. You want to work at a high speed with your blasting equipment, but avoid paint removal and peening on your metal surfaces.
When sandblasting rust, the safest way to remove rust without damaging the rest of the material is by starting with the softest sandblasting media available. Don’t use the most abrasive blasting media you can find! One advantage to using abrasive sandblasting to remove rust instead of chemical cleaners is the lack of harsh chemicals and pollutants involved in sandblasting. This will help keep the powder coating intact during rust removal, which will result in a more dustless finish and a more non-toxic process.
For gentle rust sandblasting, ground walnut shells are a soft and environmentally friendly sandblasting option. Walnut shell sandblasting media does not blast the metal, but for some heavier rust jobs, walnut may be too soft to come through and you may need some upgrades for a high performance, heavy duty sandblaster that will remove all contaminants.
Aluminum oxide is another gentle abrasive; in fact, aluminum oxide is so gentle that it is used on skin for microdermabrasion. Aluminum oxide packs nearly the power of stronger abrasive sandblasting media like glass beads, but is considerably cheaper than other forms of sandblasting media. However, aluminum oxide is not biodegradable and must be disposed of properly after use. If you’re looking for an easier, recyclable method, this may not be the substrate to use.
Silicon carbide is another popular anti-rust abrasive used both in sandblasters and in abrasive rust-cleaning creams. Silicon carbide is more expensive than aluminum oxide.
Stronger abrasives for sandblasting include glass beads and steel shots. Stronger abrasives can be used on cars with thick metal panels that are resistant to damage from the stronger abrasive media.
Steel shots are tiny balls of steel used as an abrasive; they can also be called steel grits. These materials are generally not recommended for removing rust because they are overkill—the strength of the material will remove the rust, but it could damage the metal. But if you have been unable to remove rust with a gentler form of sandblasting media, step up to a stronger form of sandblasting media to finish the job.
No matter what you do, make sure your chosen media is dry before sandblasting. Media that are even slightly damp can clog your sandblaster and stop up operations. If you are using a compressor-powered sandblaster, keep your compressor way out of the sandblasting area to keep from getting even the smallest amount of sandblasting media caught in its intake. This is especially important when the media you use is very fine and can stick to your clothes or blow toward the compressor.
Consider Your Distance
Standing too far away from the item being sandblasted will leave you feeling frustrated as you won't see the results you are expecting. Siphon sandblasting is most effective at close range, so it is important to have the tip of the blasting gun close enough to the item being blasted to allow for the abrasive nature of the blasting medium to be effective. Siphon blasting works well on small part items that can receive a concentrated spray from close range.
Use the Correct Media
Not all sand is equal in the world of sandblasting. The sandblasting industry as a whole has moved away from using sand at all. Instead many sandblasters use other abrasive material such as plastic beads or crushed walnut shells. When using a siphon sandblaster, choose a light blasting media. A siphon sandblaster has limited power because of the non-pressurized system. If the blasting media weigh too much, more of the blasting power will be lost. Crushed walnut shells, corn cob grit and plastic beads are all good media to use with a siphon sandblasting system because they are lightweight and travel well from the tip of the blaster.
Some siphon sandblaster systems are built into a cabinet where the operator can slide his hands into gloves that extend into the cabinet and sandblast small parts. The blasting media falls through a grate at the bottom of the cabinet and is collected in a tray. The advantage to this is that the blasting media can be collected and used again. It is also possible to recover some of the blasting media if sandblasting outside. Siphon blasters won't spray the material very far, so if the pieces are placed on a large tarp prior to blasting, most of the blasting media will remain on the tarp.
Plan Enough Time
Using a siphon sandblaster is not the fastest method to complete a sandblasting job. It is important to allow enough time when using this type of sandblasting equipment. Small parts obviously won't take as long to complete as a whole vehicle, but failure to plan the time accordingly could result in stress and tight deadlines. Siphon sandblasting equipment is not the best choice for time management if you will be sandblasting several large parts or refinishing more than one car, for example.
Heather Bliss has been writing professionally since 1998, specializing in technology, computer repair, gardening, music and politics. Bliss holds an Associate of Arts in journalism from Moorpark College. She also has a Bachelor of Arts from California State University, San Marcos, completed with a focus on music and performing arts technology.