Acid dipping

Zeke · 06-11-2006, 02:29 PM

We've all heard the pros and cons of acid dipping. I've had established restorers tell me that no way will a restoration survive the lurking effects in the pinch seams, etc. What I'm looking for is empirical or historical evidence that this is true, Anyone have a 10 year old acid dip? Anything, doesn't have to be a p-car.

Of course the local acid dipper says his phosphate treatment forever neutralizes the acid. But, the local sandblaster told me he's never warped a panel yet. Yeah, right, the 1st thing he did for me was a near disaster.

DUK · 06-11-2006, 02:58 PM

Milt, I've seen the reoccuring damage and it ain't pretty. I work with two guys who've done this and both have had problems. The one camaro was even "pickled" for 24 hours. It's yellow in some places, brown in the others and even worse the bondo is coming loose. These two cases convinced me to not do it. Maybe if it's a racecar, but not a street/show car. Even called three places in my area and not one would do it. PS i'll try to get a picture or two for you.

lateapex911 · 08:14 PM

I saw Boyd Coddington do it on "American Hotrod", and was surprised.....

It worries me. Just getting all the blasting media out from the cracks is a never ending nightmare. Maybe Boyds client demanded it...seemed odd to me.

Individual parts, bumpers, etc, sure..but whole chassis? no thanks.

Jim Garfield · 06-11-2006, 04:50 PM

If I remember right George K did this to his orange car and has had no issues. I would check with him.

GeorgeK · 06-11-2006, 04:59 PM

Yup, 8 years now and no surprises. The car had 6 months to dry, and received *serious* body cavity wax, that was mandatory anyway to treat all the stripped cavities.

Jim Garfield · 06-11-2006, 05:12 PM

George, did you use Waxoyl to seal it?

GeorgeK · 06-11-2006, 05:14 PM

I used body cavity wax that the body shop had, specifically for ...hollow cavities where paint can not be applied.
Not waxoyl.

Noah930 · Noah930's Garage

Whatever happened to those Trans-Am Camaro's that Penske (and I'm sure others) dipped almost 40 years ago? With racing pedigrees as successful as theirs, I'm sure someone must know where they're still kicking around.

GeorgeK · 06-11-2006, 06:04 PM

I have seen the Donohue '69 car a month ago and it is still kicking a$$, perfect condition.

randywebb · 06-11-2006, 08:31 PM

I wonder how much wt. a bunch of waxoyl or body cavity wax adds?

Acid dipping the body was one of Smokey Yunick's old tricks.

Tom '74 911 · 06-12-2006, 04:43 AM

Milt - In case you haven't run across these:

chemical dipping a 911

Alkaline, Acid, Zinc Phosphate and E-coat

When I read these threads a while ago, I was really intrigued and added dipping of some sort to my 20 yr. plan/wishlist from my '74. Seems like a great, albeit possibly expensive way, to get rid of 30+ years of road grime, all the undercoating, layers of paint, interior glue and sound junk on the floor etc.... wow, imagine working on a brand new tub. . . that would be slick.

I don't remember reading too many downsides, although I've done minimal research.

Tom

EDIT: there's a powdercoating thread going at the moment that looks interesting too - although I imagine the work to get it stripped and prepped would be . . . a lot.

Powder Coating the Tub...

chris_seven · 06-12-2006, 05:17 AM

We have been 'baremetalling' shells for about 4 years now anf have the following experiences.

Grit blasting - dosen't shift underseal without using such high pressure as to risk panel damage. One in three shells were damaged by aggressive blasting. In the end we only blasted the edges of roof panels to avoid damage.

As previoulsy stated getting the media out of joints is very difficult.

We had on rally car that we still shedding media 12 months later and was a real pain. The time spent 'rolling' the shell in a jig is also a problem.

Bead Blasting. Less damage but doesn't touch seam sealers and the like in the joints and when you seam weld joints there is always a problem.
Also equally difficult to remove the media.

Acid dipping:

We use a process which the first operation is a thermal treatment used to 'de-naturise underseal and seam sealer but not hot enough to burn paint.

There is then a 15 hour buffered acid treatment, followed by a 15 hour neutralising soak which in turn is foillowed by oven drying.

Once we have repaired and full strengthened as shell (Rally Cars mostly) we then E-coat the body (Plastic coating would be great but unfortunately all Rally cars need some repair during their life).

The E-coat process we use is identical to that applied to new body panels sold to the repair trade. We E-coat before we fill minor dents and areas wher new panles have been fitted.

Processed in this manner the shells are easy to work on have no residual material left in the seams and after 2 years none of our shells are showing signs of corrosion in the seams.

The cost of this processing is about $2000 incuding doors, bonnet and engine lids. Commercially this is much cheaper for our customers as we don't have to spend seveal hours removing media nor do we have to spend several days scraping underseals.

The company we use specialise in competition cars and take brand new shells from the production line and dip then for companies such as M-Sport and Prodrive for preparation as WRC cars and have excellent quality standards.

lateapex911 · 06-12-2006, 07:40 AM

Great post...but what is E coat? ...Electroprime? Etching primer?

Zeke · 06-12-2006, 10:55 AM

Quote:

Originally posted by lateapex911
Great post...but what is E coat? ...Electroprime? Etching primer?

I think it's electroprime, if that's the word for it. Not just an etching primer.

Thanks much for the info so far. Sounds encouraging if one finds the right person.

One restorer I know hand strips as much as possible and then sends the tub off to be touched up with sandblasting, thereby avoiding any panel damage. If you have the space and the means to catch all the crap, you can spray paint remover all over the area, let it sit and water blast it off. You need a chemical suit or a diver's rig!

I would think that hand stripping the undercoating and paint is good for a reasonably good car. The early cars I see have too much rust in inaccessible spaces. Products meant for local treatment don't seem to get the job done.

Maybe I don't understand the rust "conversion" process. Treatment after treatment still leaves a black (assuming this is the phosphate compound) stain of the metal. And it seems if one does even another treatment, some orange rust can be brought up form the pores.

When does it end?

chris_seven · 06-13-2006, 12:20 AM

The process we have used is Cathodic electrophoretic paint.

The sub-contractor that we use applies an etching primer and the finish obtained is excellent and makes final painting much faster.

When we dip 911 shells we usually remove outer sills and take out the heat exchanger tubes. We have a fixture that we bolt in to cross brace the door apetures to be certain that the shell doesn't sag.