media blast or acid dip. pros/cons

[X-Faktory]

My 71E is dismantled and ready for paint prep. It is as straight and rust free as they get. i'm tempted to media blast the exterior down, trunk and engine compartment down to the metal. (trunk has minor surface rust in the battery boxes and a little on the pan. Engine compartment firewall coating is cooked.) This car appears to have had an engine fire at 88K miles and then stored indoors in Arizona. The pans, doors, fenders body are all very, very straight and rust free.

Some folks say acid dip, some say media. I'm leaning towards media blast, but i thought I'd like to hear frome others.

regards,

al

[Gearbox]

Media blasting will generally make the exterior panels wavy unless you use the soft plastic beads which will take forever. Your probably better off using aircraft paint stripper or a DA. Submerging the entire fender or door in acid is ok if you can fully neutralize all the acid afterwards, but you'll need to repaint all the nooks and cranies under and inside the part. If the underside of the panel is good, why remove it? I'd go with Stripping with aircraft stripper and then sealing it with an epoxy primer like DPL80. I would also spray the fire damaged area (after stripping it to bare metal) with POR15 silver as the metal may have sustained excessive heat and will be prone to rust up quickly after refinishing. Good luck, just finished my 71S and it's a blast to drive.

[super9064]

Look into soda blasting. The process uses bicarbonate of soda, It dissolves in water, so it does not leave sand like residue, it does not warp the metal. It just removes paint. It also leaves a rust inhibitive coating, till it is washed off, so you do not get a flash coat of rust while you are waiting for the paint shop. The draw back is that it does not remove rust, or bondo. May not be a problem in your case. Often the sand blaster needs to be brought out the take care of hidden rust. The price I was quoted was about $600-$1000. The body shop I use charges about $85.00 an hour and would take at least a week to strip the car. The math works in favor of soda blasting. IMO

[Sacto S]

Dust, dust and more dust! You will be cleaning up dust and grit for weeks, months, if not years. The sutff works it's way into every little gap you can imagine. This dust and grit can really create problems for the painter. If your starting point is as clean and dry as you stated, I would opt for aircraft stripper and a DA over blasting. You have more control. When they media blast the lead work done at the factory gets chewed up. Aircraft stripper will not damage these areas. You may want to do a combination of treatments. You could chemically strip the majority of the body and use blasting for only the burned areas. If the underside is in good condition, why dip?

[Guru]

Have you heard of dry-ice blasting?

I'm about as far from an expert as you can get, but my car's restoration is just getting under way, and my restorer is having this treatment done at the following place in Stuttgart, which apparently pioneered the method:

http://www.carblast-stuttgart.de/

Sorry the site is only in German, maybe a Google search would bring up similar English pages.

Hope this helps...

Guru

[sithot]

This is one outfit here in the USA.

http://www.coldsweep.com/

From what I have read the equipment is very expensive.

Tom

[Neunelfer]

I've acid dipped a (66) 911... n-e-v-e-r again.

There are spots the acid will seep into that you cannot get it out (passengers foot well area.) They weep for years.

Media blasting does not warp panels, matches don't cause fires and guns don't kill people. People who don't know the proper technique warp panels.

Find a soda blaster that knows what he's doing. It won't chew lead and it can easily be blown out of the nooks and cranny's.

Trust me... I've dealt with acid first hand on two occasions and got the same results. My friends 914-6 chassis weeped so much that the body shop charged an additional two days to clean all the weeping seams.

All that being said, there are supposedly new non-toxic dipping applications that I've yet to experience. I believe Joe O'Brein at Series9 in Albuquerque had a couple tubs done. Also, it looks as though the factory restoration facility uses some type of dip tank (check the long body link here somewhere). I've had nothing but problems with acid.

I've heard nothing but glowing reviews on many friends cars that have been soda blasted.

[rick2]

A side note, has anyone done a powdercoated tub after the process?

[sithot]

If the oven is large enough it could be done but I'd worry about full coverage. A frame is easy. You pre-heat everything to get the powder to go places it normally wouldn't (Faraday Cage).

I know where there is an oven big enough if you have the money.

Best,

Tom

[boba]

Another option is to bake the tub. This will remove all paint, undercoat, seam sealer, lead. After bake the tub is lightly blasted to remove all ash and washed with a phosphate solution to stop rust. The photos are of a 67S tub, a 964 backdate to 72, and a 84 turbo. The turbo was baked, then the interior, underside, trunk, and engine compartment were powder coated. The car then went to paint. After bake the doors, lids, fenders are sent to ecoat. A facility to ecoat the entire tub has been located and some cars will be sent soon to see how that works out.