Paint Stripping - The Naked Truth

Blasting & Stripping That Old Paint From our Car

Bob Mehlhoff Jan 23, 2006 0 Comment(s)

Walk along the aisles of any car show and you'll see it: Lots of cars with paint jobs that appear fine, as long as you're several feet away. Then there are a couple of cars that look just astounding--especially up close. The sides on these masterpieces look like mirrors, with the paint seemingly miles deep. What's the difference? Well, much of it begins with the preparation before the paint color is even chosen. A typical "just bought" used musclecar today will wear at least one or more paint jobs completed years ago, when the standards weren't as high, or suffer from years of weathering, which may have allowed rust to form. In some cases there may be hidden bodywork that really could have been done a little better and, of course, a few paint chips here and there. The bottom line is if you're getting ready to invest months of work and your hard-earned money to repaint your car, you'll want to start by scrutinizing the panels and removing any ailing paint, rust, or marginal bodywork beforehand, not just painting over it. For the project warranting a completely clean body, media-blasting, chemical-dipping, sandblasting, or stripping the existing finish to bare metal is the best place to begin.

To address this, we'll explore the potential pros and cons of the various methods. But what's important is that with the proper research and application, each of these processes can be managed to provide excellent results--if suited properly to the individual car's restoration. To show what's involved, we followed along with our friend Ed Zinke, who had his recently acquired '64 Malibu SS convertible media-blasted. Although the car had experienced loving care since new (he purchased the car from the original owner), Ed's Malibu had the common rust in the trunk, universal parking lot bumps, and had at least one repaint during the '70s. Since Ed wants his Malibu's paint to glow with a deep, lustrous shine, he decided to start from scratch and take the convertible to the experienced folks at Abrasive Finishing Company (AFCO) in Gardena, California, to get media-blasted. To strip the old finish off the Malibu, the guys at AFCO use a process called walnut shell- blasting on the outer body. Walnut-shell media is comprised of ground walnut shells processed into particles smaller in size than Grape Nuts cereal. Inside the floors and trunk they found small amounts of rust. To clean these areas AFCO uses a DuPont product specifically designed for media-blasting called StarBlast.

Choose Your Media Accordingly
We'll give a short rundown of the options available, but you'll want to contact an experienced body shop, as well as the media-blasting shop, to find out what they recommend for your car's specific needs. It's also a good idea to ask people at various car shows in your area who have already been through a media-blast or chemically stripped process to learn how pleased they were with their results. And be sure to find out what their cars required prior to the treatment. Keep in mind that criteria including existing rust, metal thickness, and shape are all important factors when choosing the right media for the job.

Take it Off
The first step to getting a car ready for media-blasting is to take off as many parts as possible. You'll want to do this for two reasons. First, trim and other items left on will keep the existing finish from getting completely stripped clean. Second, parts left on may be damaged during the paint-removing process. On Ed's Malibu, he began by removing the complete interior, all the glass, wiring, the engine and transmission, convertible top, and all the body trim and chrome. If you want to do a more thorough job, it's highly recommended to remove everything. This means the doors, fenders, heater box, core support, and sometimes the frame. Since the items you have removed should be blasted too, you'll want to disassemble them as well. Generally, the more you remove, the more areas can be blasted thoroughly.

Blasting
As mentioned, there are many forms of blasting to remove paint, such as walnut shells, sand, plastic, Starblast, and baking soda. Generally, the softer the product, the less likely it is to warp or damage the metal. But it must be mentioned that if the equipment operator is not properly trained or blasts any type of media (no matter how soft) improperly, the body can be warped. This is especially true on large, flat hoods. Bottom line, play it safe and use a good media-blasting shop with lots of experience and good recommendations from both car owners and body shops. There are plenty of media-blasting shops that perform excellent work.

In a Nutshell
Walnut shell-blasting is very popular because the media is soft, relatively easy to clean up, and is not abrasive after the blasting is completed. If your body has even minimal rust, though, chances are the walnut shell will not remove it. In cases like these, you may want to consider something more aggressive for these areas. Or sometimes after the car is walnut shell-blasted, you can go back with a small rotary disc and remove the rust. Plastic media is often used because it is not abrasive and is derived from the same material most plastic buttons are made from, but like walnut shell, it will not remove rust.StarBlast is a general-purpose staurolite abrasive used frequently to remove paint, as well as light amounts of rust, from automotive bodies. The grains are uniform in size and have clean, rounded surfaces so they do not damage the metal (if blasted properly). This media works by knocking the paint off--instead of cutting it off like harsher medias.

The Sand Man
True sandblasting has been around for decades, and is typically best for thicker items with rust. These would include frames, brackets, and older, thicker, and rigid sheetmetal components blasted properly. Here extreme caution should be used because the sand particles can peen, stretch, or warp the sheetmetal. Sand is sharp and unforgiving, and consequently, the operator must use extreme caution when blasting. Whenever sand is used, it is best to remove everything possible from the body (i.e., window regulators and drivetrain components) to avoid damage after the vehicle is put back into use. Then, as with all media-blasting, the remaining product should be blown or vacuumed out of the body. The media removal process (no matter what is used) can take several hours (or days) to complete.

Chemical Removal
Hot tank-stripping or chemical-dipping is a very effective way to remove paint and rust. Entire car bodies can be dipped into a tank for several hours, and the caustic solution will flow into areas where a media-blaster would never get. Chemical-stripping typically leaves the item looking fresh and clean and ready for the body shop. There are a few concerns to this process that should be mentioned. After the paint or rust is removed from unexposed areas (such as bracing inside of a car body or a hood), there is no way to paint or treat the hidden bare metal, leaving it vulnerable. Second, all the chemical must be removed (and sometimes treated with metal conditioner) so that it does not weep into the new paint or primer. Finally, if you have any aluminum items, do not have them chemically dipped, because the caustic solution will ruin them.

Hand-Stripping
Hand-stripping is great at removing paint and some body filler. If you're concerned about the possible problems associated with some forms of media-blasting, hand-stripping will allow you to remove all the old paint, but the entire car will not come totally clean as with media-blasting. When using any hand-stripping product, be sure to remove the old stripping solution completely from the crevices and metal surfaces. Otherwise, the remaining paint-stripping product will come to the surface and ruin the final paintwork.

Power Sanding
In many cases, you can remove most of the old paint and some existing rust with a power sander. It's labor-intensive, but can be done almost anywhere and will only cost you the price of the equipment, sandpaper, and power to run your compressor. Again, this process will only work on areas the sander will reach.

Conclusion
Before tackling any media-blasting or paint-stripping job, decide what your goals are for your car. Next, talk with an experienced body shop, a media-blasting facility, and others who have had their cars stripped. In some cases, you may want to use a combination of the processes described here. If you're planning to replace any body panels, ask your body shop if that should be done before or after media-blasting. Remember, there are no rules that apply to all cars. In the end, whatever route you take will contribute to making your car's body and paint a true prize in anyone's eyes. That's worth it at any distance.

11

Before blasting, Ed removed much of the trim, the convertible top, the bumpers, the drivetrain, and the dashboard components. The 30-year-old second paint job had some flaking, and inside the trunk a little rust had formed from a small leak in the convertible top.

Inside the blasting booth at Abrasive Finishing Company, Jesse is ready to blast off the old finish. The booth serves to control the environment while the car is blasted and keeps the dust from the surrounding atmosphere.

So that the media does not warp the metal, a properly trained professional using the correct air pressure, equipment, blast angle, and media will ensure excellent results. In other words, don't try this at home, and don't have someone try to learn how to do this on your car.

This interim shot of the door after a few moments of walnut shell-blasting demonstrates how the paint is stripped from the door.

A common find during the process is unearthing a previous repair. Years ago, body shops would typically drill holes and use slide hammers to pull dents from sheetmetal. Then the holes would be filled with plastic body filler and sanded smooth. Today, a Stud Welder System spot-welds pins to the surface of the metal that are then grasped with a special puller to remove the dent without drilling holes. Making modern repairs to this type of discovery is one of the reasons it's a good idea to strip a car to bare metal prior to a quality restoration.

The area under the hood is blasted as well to get as much of the finish off the car.

Even the inside floor area will be blasted to remove the old finish. But in this case, StarBlast is used to remove small amounts of surface rust.

Inside the trunk, moisture had accumulated between the trunk mat and trunk floor, which rusted the area. Because the walnut-shell media will not remove rust, AFCO hit the area with StarBlast to remove both the paint and the small amount of surface rust. StarBlast knocks the scale off without harming the metal. Some media-blasting shops use StarBlast on the entire car body (inside and out) with great results. Again, it depends on the particular car's needs.

To completely media-blast a car takes several hours. The next step is to blow the car out as best as possible. Once at the body shop, it will be blasted out more thoroughly.

With the car in bare metal, it's best to go to the paint shop for prepping and priming within 24 hours, not just transported and parked inside the body shop within 24 hours. Make sure you coordinate this schedule with both shops before the car is blasted. You'll also want to keep track of your local weather forecast (and your work schedule) to make sure your car is not caught in a downpour on the way to the body shop. If you contract the transportation part out, be certain to be along for the trip and make sure no one touches the fresh metal--especially with greasy hands. Remember, rust loves bare metal, especially when it's humid, cold, or rainy. Don't rely on your good luck.

The firewall and frame of this '69 Chevelle have been plastic media-blasted. Although all the paint has been removed, a close inspection reveals some minor surface rust the plastic media did not remove. On this particular car, the small amount of rust is not really a problem. Most of it may be removed by treating the bare area with metal conditioner. If the rust were more extensive, other blasting options would have worked better.

Here the left hand is holding plastic media...

...and the right hand is holding walnut-shell media.

In some cases, entire vehicle bodies are dipped into a chemical tank to strip away the paint and rust. Often stubborn areas require removal with a putty knife (after the dipping tank has softened the paint) to clean everything away.

The before and after shot of this '67 Camaro's core support's lower right section reveals how well chemical-dipping can clean and remove rust...

...After years of leaking batteries and moisture, this core support rendered clean with a chemical bath.

Jorge at L&M Strippers in Van Nuys, CA, pulls a vintage sheetmetal hood flank from a stripping tank. This process usually takes a few days and will completely clean the old paint and rust from the item.

COMMENTS

subscribe to the magazine

get digital get print
TO TOP