Cleaning rust from an old car? Try sandblasting

There are some cleaning and restoration jobs around the garage that are too tough for detergents and elbow grease. A rusty leaf spring on a vintage vehicle, a wheel ravaged by road salt and brake dust, a dingy accessory on an otherwise sparkling engine—when it comes to this kind of hard-core work, savvy DIYers bring in the heavy artillery of sandblasting. (It’s also called media blasting, though sand is no longer used due to the health risks of inhaling silica particles.) Sandblasting can strip paint without damaging the base material, even if it’s plastic and wood, and smooth out pitting on the hardest of metals. The technique’s utility extends to other home projects, including stripping old bike frames and metal lawn furniture, and even removing calcium deposits from tiles.

The operation uses pressurized air to shoot tiny pieces of material (media) out of a nozzle to strip off the surface of a target. It’s like pressure washing, only at lower pressures and with projectiles that are a lot more abrasive than droplets of water. The most commonly used media include plastic beads, ground-up walnut shells, glass beads, and aluminum oxide.

To media-blast at home, buy a blasting cabinet to contain the mess and to avoid covering your entire garage with a fine dusting of walnut shells. The cabinet usually consists of a closed box with a blasting gun and a pair of heavy-duty gloves built into the structure. For less than £200 you can get a bench-top unit with a working area of about 22 x 18 x 12 inches. Larger self-standing cabinets with about 6 cubic feet of covered space are more expensive—as much as £1500 and higher. The media generally cost less than £50 for a 5- gallon bucket, and most media can be reused repeatedly. The other requirement is an air compressor that can handle a minimum of 80 psi at 5 cubic feet per minute (at least £200 if you don’t already have one). For larger objects, such as wheels or body panels, you can build a simple enclosure with 2 x 4s and plastic sheeting, although that also requires a handheld gun and personal protective equipment. For bigger projects, such as a car frame, it’s best to hand the job off to a professional shop.

Even though sandblasting can strip the chrome off a bumper, it’s not very good at removing grease. Before you blast, make sure anything sticky or oily has been cleaned; otherwise, you’ll end up immediately fouling the media you just bought. The rule of thumb for sandblasting is to use the lightest abrasive and lowest pressure necessary to get the job done. Don’t forget that the softer the target material, the gentler you need to be. Always test your material and pressure setting first on a section of the part that isn’t seen. Heavy media often leave a rough finish, so keep in mind that further polishing steps after blasting may be required.

You also need to watch out for flash corrosion, which can occur when moisture in the air rapidly oxidizes a newly exposed piece of metal. If this is a risk (don’t do anything when the humidity is above 75 percent), be ready to treat raw metal with primer paint or another protectant as soon as possible. You don’t want your shiny new surface to vanish under a fresh coat of corrosion.

The Nitty Gritty

Different types of common blasting media produce very different results. Plastic beads and walnut shells yield almost identical results. Walnut shells are dirt cheap and eco-friendly (perfect if you’re doing work outdoors) but only last for one use. Plastic beads can be used multiple times. Both are gentle enough to strip paint and remove minor blemishes on metal, although they aren’t abrasive enough to remove all the rust shown here. To do that you need to use glass beads, which stripped away enough of the metal on our bar to make it look fresh again. The last section shows why aluminum oxide is the 800-pound gorilla of blasting media. If you want something clean, it’ll be clean right now, and aluminum oxide can even smooth out scratches and gouges. The extreme hardness of aluminum oxide means that its effects last a long time, and it’s generally pretty inexpensive. It also leaves a coarse finish, as shown by the dullness on the right end of the steel bar, compared with the middle section.

Safety First!

Microscopic dust that results from blasting is bad for your health, so when working on large projects, be sure to cover up. We recommend: a face shield and/or safety glasses, ear protection, and a breathing mask. A handheld blasting gun requires gloves, and an apron is a good idea. The blasting cabinet is downright tidy in comparison, but it limits your work space.

If you’d like to get your car parts sandblasted, contact New City Sandblasting, who are number 1 for sandblasting in Preston.

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