Seeking Opinions and Experiences Concerning Dipping vs. Blasting?

Blast it...

Both have their drawbacks. As mentioned, dipping or painting chemical strippers on can allow the chemicals to work their way under a Pantera's separate body skins and frames, to come back out during or after painting, ruining the job.

Blasting fills crevices in the monococque with dust so that almost regardless of what you do to blow it clean, air pressure from the gun during paint spraying will loosen a few more particles, again ruining the job.

When I stripped our car to bare metal some decades ago, I used thick Aircraft Stripper to within 1" of the edge of each panel. The last 1" around each panel got sanded off by hand. Worked for me....

We used a DA sander with 80 grit to take it all off.  In my case there was only one additional paint job done to the car.  Areas that had filler took more time.

What about the effects on the parts of the car that you can't see?

There are hidden channels and crevices that you can't get to with a sander or a sand blaster.  If you dip and then e-coat you have stripped and (importantly) protected those as well.

If you don't dip it, you have to either rely on whatever the factory put on the car in those areas (if anything) or top that with something you blindly squirt out of a nozzle on a wand.

Does the e-coat step eliminate the worries of the stripping solution lingering and ruining the paint later?  Or could that still linger and ruin the e-coat + paint job?

An alternative to both blasting and dipping is to strip the paint using a Contour SCT surface conditioning tool by Eastwood Auto Restoration supplies. They do a great job and are very fast. It takes about 10 minutes per panel to strip the surface down to the bare metal. The metal is left with a surface finish similar to an 80 grit DA sanding. The wheels are sort of soft so they don't do any damage to the character lines. The best part is, no blasting grit or messy chemicals left behind. Good luck with your project.

Dry ice blasting. No residue.

I would agree with Jack, do not media blast.  I did it, took forever to clean out the rocker panels.  Even now, years later, media "snows" from some of the channels.

Dry ice would be the low touch option.

I believe which way you go depends on why you're doing it. If rust is your concern then dipping is the answer. It gets rid of everything that isn't solid metal. I had my Pantera dipped about 20 years ago because I was concerned there was rust where I couldn't see it; inside frame rails, etc.  Modern dipping techniques are great at neutralizing all the chemicals and then protecting areas you could never reach. To this day, I've never discovered a single spot where one of the chemicals used in the process leaked out over time.  

My Pantera came out of the chemical bath as a clean shell with only a couple of rust spots in typical areas such as a silver dollar sized hole one rocker panel and some small holes in the rear, inner fenders. I've seen other Panteras dipped that didn't fare so well. I saw one Pantera that came out of the tank looking like a lace doily. Literally every panel was full of holes. The owner wasn't a happy camper! 

perryh posted:

The older threads seemed to (mostly) reach the conclusion that the dipping path was leaden with treacherous potential side effects that could ruin a restoration years later as un-neutralized acid creeped out, ruining paint jobs, or bare metal that could not be reached with new paint.

That was the experience of a former co-worker. She and her husband restored an Austin Healey Bugeye Sprite and had it dipped.  Within a year or two of driving and showing the car on hot days, residual acid managed to leak out of crevices and onto painted surfaces ruining the finish.  They swore they'd never dip a car again.  Perhaps if after the acid bath it could be dipped and agitated in a neutralizing rinse solution it would prevent such an occurrence.  

Garth, in fact, professional auto dippers not only have such a neutralizing rinse, they follow that process with a galvanic primer coating, that finds its way into places that cannot be seen. 

It's important to use a business that specializes in automobile restoration dipping. They know the pitfalls and how to eliminate them. Most dipping facilities specialize in industrial applications. For obvious reasons, dipping a fence or a boat anchor is much different than dipping a car. 

davidnunn posted:

Garth, in fact, professional auto dippers not only have such a neutralizing rinse, they follow that process with a galvanic primer coating, that finds its way into places that cannot be seen. 

That sounds good.  I think the neutralizing rinse my friend's Bugeye received was a spray wash after coming out of the acid bath. I like the idea of a galvanic primer coating all inaccessible interior spaces.

For the europeans:

http://carblast.de/chemisches-entlacken/

I will have 4406 processed by this company as soon as I finish the body work, in a few weeks.

The risk of acid remaining is now well controlled, but there is another disadvantage, it also dissolves the tin / lead and there is many on our Pantera that will have to redo.

I think it's best to have it done before doing any bodywork because dipping might reveal an area that needs work. In my case, it did not remove leaded areas. It did remove rusty metal, paint, primer, undercoating and bondo. Oddly enough, it did not remove all of the black, tar coating on the inner fenders. That is tough stuff! 

Before or after, both have advantages and disadvantages.

Doing the body work after destroys the protection by cataphoresis in all the areas where it is necessary to weld and the new pieces of sheet are protected also by cataphoresis, but it is true that we can also discover other areas to be repaired that had not been seen before.

I had my car acid dipped, neutralized and e-coated almost twenty years ago.  I have not had any paint issue with the process.  The acid does eat white metals, like lead, so you will need to re-lead or plastic fill certain areas of the body.  All body work was done after the dip and e-coat.

If your car comes out of the dip tank looking like a lace doily, it is probably better to know it all now, rather than sequentially finding each spot that rusts from the inside-out.  The dip tank is a truth teller— no rust can hide!