Sandblasting,
"The Dirty Truth"

WHEN STRIPPING A CAR TO BARE METAL, it’s critical to select the proper method of stripping. Otherwise you’ll end up with a car that’s less than ideal – either with damaged metal, or rust still hiding underneath the paint.

First, let’s look at why cars are stripped. There are two main reasons:

– Remove previous paint and body filler that will later fail
– Remove rust and clean the metal to prep for new coatings

If a car is repainted on top of previous paint, that paint with its chemical composition (frequently lacquer or enamel) is often not compatible with high-quality restoration paint (urethane). What happens next is not pretty: chemical reactions that sometimes take weeks to happen, wrinkling up the paint, causing lines and rings to appear, and even making old paint soft so you can push a finger right into it.

In addition to old paint, if old Bondo is not removed prior to repainting, the Bondo is likely to crack and separate from the car at some point, leaving chunks falling off the car. This is why it’s important to remove all previous coatings from the car, to guarantee a long-lasting new finish.

The most common method of stripping a car is sandblasting. This is also called “media blasting” if it’s done with walnut shell, baking soda (called “soda blasting”), glass bead, or other material instead of sand. Sometimes glass bead is used with water, called “hydroblasting” or “water jetting”. Regardless of the material and the method of blasting, all these types of blasting have some major limitations and risks.

The primary danger with blasting is damage to the metal. The pressure and heat from blasting causes warping and stretching of the metal. This defeats the purpose of removing old body filler – since new filler will need to be used where the metal was compromised. Even the most skilled sandblasting technicians leave behind metal with warp and thinning.

Water jetting avoids the heat but leaves muddy cakes of wet glass bead in corners and crevices in the car, causing rust. Soda blasting is more gentle, but as a result does not remove previous coatings as effectively. Also, the car needs to be washed after soda blasting – which causes flash rust.

The biggest flaw in sandblasting, however, is not what we’ve mentioned so far. The biggest flaw is that sandblasting cannot reach the most problematic areas where rust grows. Imagine this: hidden cavities in a car – such as the rocker panels, bottoms of doors, bottoms of quarter panels – are exactly where moisture collects, causing rust. And those are the exact areas that cannot be reached by sandblasting. There is no way to shoot sand all around inside those cavities.

That’s not to mention the seams between pieces of metal – like the seams where the floor pans connect to the transmission tunnel or the rockers. Those flanged areas where pinch welds hold panels together are where rust hides, inside the seams. Sand and other media can never reach there, to remove the rust.

So the result of sandblasting is a car that looks on the outside like it’s bare metal, shiny and clean. But inside all those cavities and seams, rust is left to grow, eating the car from the inside out. That’s the dirty truth about sandblasting, and it’s one of the most common pitfalls in classic car restoration.

For the discerning car owners who want a proper restoration – a car that’s like new – what’s the solution? How do we bring a car’s body back to being like new with no rust, and avoid the damage left by the various blasting methods?

At Evolve, we use a completely different method for stripping to bare metal: a three-stage chemical dip process. This process completely removes all previous coatings and all rust – inside cavities, inside seams, anywhere it’s hiding: in the roof, the fenders, the headlight buckets, the dash, the trunk, everywhere. And it leaves the car’s metal clean and undamaged.

Here’s how it works:

Tank 1: Chemical stripper. The entire car is lowered into a vat of heated, aggressive paint stripper, and allowed to soak for sometimes several days, until all the previous coatings are stripped.

Tank 2: Acid. Next, the body is removed from the stripper, pressure-washed, and submerged in a bath of acid. This acid eats away the rust corrosion, while leaving the steel perfectly untouched. Every little area of rust is submerged and neutralized by the acid – areas that no other method is able to reach.

Tank 3: Rust inhibitor. Finally, the shell is lowered into a bath of rust inhibiting chemical, to prevent the newly-cleaned steel from flash-rusting. This chemical solution also neutralizes any remaining residue of acid, to prevent later leaching or chemical reaction.

Following this three-stage dipping process, the entire car is sprayed with epoxy sealer, which is the most durable primer to use on bare metal. The insides of the cavities are coated with cavity wax to hermetically seal the metal, and prevent rust. Then the various layers of primer and paint are applied, to further protect the metal.

That’s how to prep an automotive body for proper restoration back to new condition. And that’s what we do a