Options for stripping tub to bare metal?

[Tom '74 911]

Hello -
I've read about a few options for stripping a tub to bare metal, but am still wondering about the easiest, most economical way - I know it's hard to use those two words in the same sentence! Economical, of course, could be related to time, money or some other factor. I'd like to compile a list of the options and the pros and cons of each if possible w/input from people that have actually used some of the various methods. Gunnar Racing has an awesome pictorial summary of a bunch of their projects like the Ratt (see projects completed) - They used LOTS of elbow grease.

My ultimate goal is to strip my entire car to a bare metal tub - remove all 3 coats of paint, all the undercoating and interior soundproofing on the floor etc... so I can start from scratch. If this ever actually happens. . . well, we'll see, but I hope so.

I'd like to be to see all the trouble spots that exist and be able to fix them. I would hate to sink a bunch of time, energy and money into my engine, suspension, electrical system etc... only to find out later that the undercoating was hiding some major rust areas. I don't think any 30+ year old car is "rust free". I know a project like this doesn't make economical sense in any way - but that's not why we play w/these cars in our garages anyway.

It'd be great to get rid of everything (paint and undercoating) in one shot instead of spending a years worth of hours w/a grinder, heatgun, razorblade, paint stripper chemicals, sandblaster etc... but maybe those are the best ways? Maybe combining a few of these is the best? A big plus to these options are that I can do them myself, or have someone w/in a days drive help (sandblasting).

Sandblasting:
I know there are lots of different media to use - which is the best? I've read that sandblasting won't touch the undercoating. I've also read that sandblasting will warp panels like hoods and roofs.

Baking:
I'm not really sure how this works other than putting the tub in an enormous oven set at 700 deg. for a while. Does all the paint and undercoating get reduced to ash? Is this a readily available solution?

Acid dip:
I've found some threads on this:
Acid dipping thread #1
Acid dipping thread #2
This process seems expensive and maybe still controversial as far as the long term effects of not getting all the acid out of the nooks and crannies? But it does rank high on the "easy for me" scale - assuming I don't have to drive for 3 days to the nearest place to get it done.

My last question centers on the best way to treat the bare tub once it's stripped. Durability is probably #1 here. I don't want to care if it's raining or snowing out when I get in my car to drive it! Powdercoat, epoxy primer, spray in bedliner, Por 15. . . something else? Also, after either baking or an acid dip, I'm assuming that all the paint or whatever protective coating and seamsealer exists in the hidden nooks and crannies (like the inside of the tunnel and rocker panels for instance) is gone. How do these areas get re-protected?

I know this is a big topic and maybe my questions are too open ended. Maybe I should just go down to the hardware store and buy a box of wire weels for my grinder and have at it?

Thanks,
Tom

[SoCal70RSR]

Tom,

Since sandblasting doesn't take all the undercoating off, I would recommend removing it yourself prior to sanblasting and epoxy primer after sanblasting. In my opinion epoxy primer is probably better then por-15. I've seen por-15 chip and the epoxy primer does not.

Sanblasting carries the danger of warping long flat surfaces (roof, hood,etc) so make sure if you have it done to use care on these areas.

[TWork]

I think you may want to change your category from "sandblasting" to "media blasting" as it's probably more accurate. Given the size of the project, I wouldn't consider media blasting an entire car to be a DIY job. I'd just tow the shell to the shop and let their expertise guide what media is actually used. I had considered having my project car media blasted. I talked to 2-3 shops, undercoating removal never came up as an issue.

[gestalt1]

if i had to do it over again i would dis-assemble the car completely, use peel-away stripper on the undercoating and have the tub media blasted. immediatly have the tub epoxy primed. the only thing i did do differently is to mediablast first then used the peel-away. the media blastiong does not remove the undercoating and i wasted time and money thinking it would. the baking idea sounds reall interesting to me also. i wonder if there is a vendor that will bake the tub and then powdercoat everything but the exterior panels.

[Grady Clay]

Guys,

I have a chassis that was new in ’72 and I stripped in ‘74.

While this is still a spare for my (my son’s) race car, it has application here. I had the chassis “dipped” in caustic to remove all the paint, under coat and sound deadening. I cut opened the tunnels to allow those areas to be free of material.

A chassis like this needs permanent corrosion protection.


PAG built the chassis with burning off the manufacturing coatings, This prepped the chassis for rusting. Taking an un-rusted chassis to preservation, requires the chassis to be preserved in-side and out-side. That is not easy.

Ideally a clean chassis could be ultrasonically cleaned and then coated with a preservation coating. How do we do this?

The disappointing part is that PAG/PCNA don’t provide original replacement parts. Come on guys, step up and provide a replacement chassis.

Best,
Grady

[Rich76_911s]

One thing to note when dipping, or baking a car (EVERYTHING) has to be removed, every wire, everything.

What car are you doing this on a '74?

It seems like the best way to do it is a combination of methods. If it were me I would chemically strip the largest portions of my car, and be cautious about keeping the stripping compounds out of seams, and tight places. After that I would take the tub to a media blaster and have them finish the final sections. In essence you do the parts of the car that are best done with chemicals, and have them do the parts that are best done with media.

I stripped a car with chemical stripper that also had 3 coats of paint. It took a long time, and was a mess, but getting a 911 to bare metal and looking at those hips in raw form knowing you did it, is really gratifying. Just hope you don't find the bondo and accident damage I found. Also if you do chemical stripping please wear HEAVY gloves, a respirator made to protect you from the aroma, and long pants and sleaves.

The year also matters because if the car is a galvanized '76 or later car then media blasting will remove the galvanizing.

Rich

[Cooper911SC]

I used a combination of methods on my '70 914. First, everything has to be apart. I bolted my car to a rolling dolly and sent it to a sand blaster...yes they used a fine #60 sand...they warped the front trunk lid. (Too high a pressure) Everything else was fine. The undercoating and seam sealer were still in the car when I got it back. The blasting seemed effective on the areas of seam sealer where rust had already started between the sealer and body. I used a spot blaster and sharp puddy knife to chip away and blast away until I was happy that I had found rust free metal. I then re-seam sealed with Wurth Body Schutze. I used Wurth Metal Prep to coat the raw metal and keep it from flash rusting whlie I did the body work. Then I used an etching primer and then an epoxy primer sealer.

I think the multiple method approach to stripping a car is the best. I would definitely recomend sending the car out for blasting...I paid $200 or $300 to have my entire car inside and out done. Saves time and a big mess. One other down side to media blasting is that you will constantly be finding the media here and there in seams and holes in the chassis. Takes a lot of blowing to get rid of it all.

Good luck, Cooper

[boba]

Do a search on "zuffenhaus" they have done numerous bake offs and powder coat of tubs. There is a better description in those posts but, first bake, then power wash ash with rust inhibitor.
First tub is a 1967 S, Bake does not eliminate the rust already there.


Second tub is a1990 being backdated to '72 RSR.

[Dennis Kalma]

Here is the results of my plastic bead blast on my '75.....did a good job, I figured that if the blasting did not take off the undercoating, it was well adhered and deserved to stay there. Second pic is the same chassis with undercoat (Sikkens OTO Bodycoat) and Sikkens primer....

No problems after 13 years, other than i still find plastic beads here and there....