[67Dan]

Bought a 67 GTO from a man in the Dallas area. Found it in Kansas and documented everything. It was media blasted, I believe using Soda. Bought it and as usual had to work out plenty of problems.

Had to store it outside covered in the sun for a while until my shop was built. Noticed two bubbles over the rear wheels on the quarter panels. That was the start of things to come. I have had the car for three or more years. So I would have thought it would be through! When I moved it to be stripped it looked like it had leprosy!

The paint got really bad, but since the performance was great, I thought let’s get it painted. Found a nice color, the paint was stripped and double primed, painted and clear coated. First day I took it out in the sun I had bubbles show up. Talk about pissed!

Plan on media blasting this time. While talking to the guy going to do the work, he talked about soda blasting cars and if they don’t clean it very good to neutralize the soda it will bubble and could be my problem.

I want to keep the car and pass it on to my Grandkids. I want it right, but I already have plenty of money in the car and a paint job that’s toast! Does anyone believe that could be my problem, or are we going down the wrong street! The blaster was taking about bead blasting.

After cleaning what do you need to use to keep it from rusting or do you just shoot it primer right away?

Help, I can’t blow more money!

[67gtospud]

When I worked at a industrial blasting a painting shop we had a lot of project cars come through. We never soda blasted them so I can't pinpoint your issue there. We always plastic bead blasted the paint off then spot blasted in glass bead. For the floor and firewall we used sand. During the 3+ years I was there we did a lot of cars and never had any issues with paint or primer bubbling or peeling. Most of our customers were repeat with new projects. If there were issues we would've heard about them.

After its blasted, shoot with epoxy primer right away. The sooner, the better.

[strato gto]

Metal should be sanded after blasting or chemical stripping.Metal should also be etched with a metal prep chemical.Then it should be sanded again before epoxy primer.I know some will disagree as this is a lot of sanding but in my opinion this is the right way to achieve proper adhesion.
When a car is bead blasted the surface can get polished from the stripping action.Some people RUSH the job into primer without sanding.SANDING IS A MUST for proper adhesion.Etching the metal with a chemical is also important.Looking at that picture of current delamination you are correct that paint job is toast.Sorry it must be stripped!

[strato gto]

Also soda blasting is the biggest culprit to this particular problem.Even though it is easy on the metal it doesn't leave a surface that primer will stick to.Sand the hell out of bare metal.Don't worry primer will fill all the scratches and because it is on metal they will never surface in the paint job.But then again primer and fillers have to be sanded correctly.

[67Dan]

Thanks for the help!

[nytrainer]

Freshly blasted metal can be a great surface to accept epoxy primer (like Rally wheels etc.) but we always buzz over any body panels with 80 grit on a DA sander.
I don't know what was used on your car but using an etching acid or even soda blasting is a big no no when using SPI epoxy primer. Since we don't use other brands of epoxy primer I can only speak of SPI epoxy primer but I would imagine the warnings would be similar (see SPI precautions on using their epoxy primer below).
Some blasters prime their work with a etch primer. Make sure they know you want to epoxy prime it (might need to supply it to them or do it yourself) as etch primer under epoxy is not recommended either.

[critter]

My brother in law had 2 of his customer's cars soda blasted by a service. Both shed paint like a snake dumping his skin. Now all cars are sanded to bare metal. Never again, he said.

[68azbird]

It's all about the Ph and following instructions.

[GOAT WHORE]

Originally Posted by nytrainer

soda blasting is a big no no when using SPI epoxy primer.

SPI epoxy over a soda blasted vehicle is fine according to Barry, the owner of SPI, as long as the vehicle is washed well. This is based on a conversation I personally had with him. If you read the warning it does not say you can't do it rather to call first.
I have soda blasted around 100 cars as well as aircraft and boats, never have I had one case of paint adhesion issues. I have however had cars come into my shop to be stripped with the same failing paint issues that the op is having.
One more thing, I am wondering why the paint stuck to these cars for 40-50 years and the factory never sanded the panels first?

[strato gto]

My knowledge and experience is limited to PPG products.They have a tech sheet [P sheets} for every product and can be downloaded to your computer for print out.Make sure the body shop that you use cares enough to even educate themselves about the products they use.My supplier says only a handful of people even understand mixing ratios or follow proper procedure.
Restoration is not collision work-use a restoration shop with knowledgeable workers who love their work.A lot of body shop workers just go though the motions with no regard to their actions.

[67Dan]

Looks like the guy I'm talking to to do the media blasting prefers plastic pellets or glass. Any preference?

[3goats]

Try dustless blasting. If you've never heard of it google it. It is glass and water with rust inhibitor mixed in the water used. Works great and fast. I did my 69 judge complete inside and out in about 4 hours at a cost of around 400 bucks.
Check it out FYI

[GOAT WHORE]

Originally Posted by 67Dan

Looks like the guy I'm talking to to do the media blasting prefers plastic pellets or glass. Any preference?

Is this car going to be completely disassembled, glass and interior out? If not your looking at some major issues including dust in all of the interior including the possibility of dust inside of the gauges. No way to get the door jambs if not disassembled.
You said the last painter took it back to bare metal, did you actually see the car in bare metal?

[JSPONT]

Yes soda blast leave a coat that does not do well with primer. Some people soda blast because it will not rust for a while even in humid areas. But that coating does not let anthing stick. NYTRAINER gave great info on it, You have to sand the entine car or da before primer. Sorry but you will have to strip,sand and repaint. Plastic bead is good and will not warp panels if done correct.

[GOAT WHORE]

Most people choose soda because it will not warp panels. If washed properly after there will be no adhesion issues. As far as that goes, a car should be washed after any type of media blasting to remove all the dust and contaniments.
As a side note, if you wash with Hold Tight 102 using an upstream chemical injector attached to your pressure washer the sheet metal will not flash rust as it dries. Same thing they use in the dustless blast system.