LIke other guys have said, the Seeping problem comes from having a half ass operation do the dip. If they do their job right, by properly neutralizing the solution and properly rinsing everything, you should not have any problems with seeping later on down the road.
That being said, I do wish these companies would take things one step farther like the new car manufacturers do and as a final part of the step, dip it in electrostatic etch primer. Most of the new car companies do that now. I dont see any reason why they couldnt incorporate that into their procedure as well.
I have heard good things about this place.
http://www.americanmetalcleaninginc.com/services/automotiveservices.html
If your on the Left coast, you might want to try this place. This is who Graveyard Carz uses.
http://www.metaldipping.com/faq.php
The cost to set up a dip primer line would be in the millions and you could never get a payback. The cost to fill the tanks is astronomical. I have worked at facilities with both plating, e-coat, wet paint and powder paint. Powder has the least cost associated with any of them.
E-coat lines have a very small amount of paint in suspension in water in the tanks. The current that is ran through the body attracts the e-coat to the metal. It will not coat inside like between hood and trunk reinforcements. Not enough flow of material inside the confined space.
To get the body clean enough to go into a dip e-coat is something you have to see to understand. There are multiple stages of washing rinsing that you could never do on an old body.
An example of how easy it is to contaminate the solutions would be at John Deere at their combine facility. You can imagine how big the tanks have to be to accept parts for the combines. Like swimming pool size. All of a sudden one day they started getting fish eyes on the finish paint. A rubber wrist band was the cause. One like they give out at benefits say for cancer or something. The amount of silicone in the bracelet was enough to cause the entire paint wash system to have to be dumped and everything cleaned over and over. Cost millions of dollars over a rubber bracelet.
At one of the other John Deere facilities in Greeneville Tenn. they build the John Deere mowers sold at Home Depot and Lowe's. The company I worked for supplied all the stampings including the fender. We get a panic call and they are getting fish eyes in their fender paint which is powder coat for the green. They sent their chemical engineers to our plant and took samples of all or our draw lubes, equipment lubes etc. We took one of the fenders and cut out fish eyes and sent to our lab. They determined that the fish eyes were caused by under arm antiperspirant and even determined the brand. The issue was not in our plant but was John Deere employees that hung the parts on the paint chain. The antiperspirant was falling out of their shirt sleeves onto the parts and the wash system would not remove all of it. So there is an approve deodorant list that the employees can use.
To attempt to run old car bodies that have had Armorall, silicone, grease, oil on them for 40 50 60 years would impossible. That is the reason they do not and will never do that.
If you do get one dipped it is best to apply primer inside the panels with a brush. You cannot spray inside the corners and seams. Nothing says you cannot apply primer with a brush or a roller. A rotisserie works great so that you can run it into the seams.
One of the bad things about dipping a car is that you loose all the mastic that they put between the inner reinforcement in hood and trunk and no good way to get it back to look correct.
Molasses does not remove paint or mastic just the rust. That is why I like it.
