Weld Thru Or Epoxy ?

Any auto body gurus here ? Wondering how the experts do it. Would you spray weld thru primer between the joints then spot weld or epoxy all the parts apart, clean spots where welding then spot weld ?

I hate rust

 

The factory would have used spot welds and over-spray everything.

I would certainly (at least) spray weld-through primer on the lap joints before I plug-welded the panels, copying the way the factory did it while adding weld-through. Then I would have better rust protection than the factory, and still secure the panels as well as the factory did.

One option is to plug-weld the panels, and fill the joints with paint. You can add some kind of MCU (moisture-cured urethane) like POR-15 or Hirsch or Aluthane, to seep in to the joints by capillary action and prevent rust. Realize that rust need substrate (steel), humidity and oxygen. If you remove any of those, the substrate will not rust. If you look at Robert's posts (MP&C projects posts on Garage Journal MP&C Shop Projects - The Garage Journal Board ), he primes the lap joints with HOK epoxy primer, then removes the primer to plug weld the joints.

So, however you choose to do it, it helps to have the un-welded lap joint parts covered with paint of some kind. Choice of paint is up to you - weld-through, MCU or epoxy primer, but adding paint in the joints seems to be uniformly thought beneficial.

 

Epoxy and welding don't play well together, at the detriment of the epoxy. High heat will destroy the bond and integrity of the epoxy. For assembing the body tub components, I would plug weld everything, duplicating spot welds. This is assuming you don't have a spot welder. I use a sheetmetal punch to make holes in one side, then rosette weld, similar to a spot weld. You could use weld-through primer before the assembly. I usually dust over all my joints with a sand blaster, then thin out some two-part epoxy primer and liberally spray all the seems before a full-strength coat of the same primer. In some cases, I have run a bead of panel bond after the over-thin primer as a seam sealer. The thin primer wicks into the lap joints pretty well.
I use panel bond for other type body repairs, but not anything with major structural joints, at least not to date.
-Donny

 

You have any trouble getting the Classic Enterprises parts to fit? I sure did.

 

After I finished welding my tub back together I had it sand blasted and painted it with Chassis Coat, like Por 15, with a brush. I painted the whole inside, under the cowl, the inside floor and the underside floor. It run flat and shinny and has held up for 11 years through sandy and gravel roads, it is just starting to wear through around the clutch, throttle, and brake are.

 

Since you will be painting everything after it is put together. I would used that eastwood undercoating in the hat channels, that stuff runs and will fill the metal where it is mated together. I would then seam seal the edgesr of the hat channel to the floors. I coated the bottom of my tub with stone chip and then base coated, clear coated it. Did the front fenders too. The stone chip filled gaps and has a orange peel texture which hides any imperfections in the metal. Painting the inside of the tub should seal all of the metal joints which should keep mositure out, if you are clear coat.

 

As a former bodyshop owner this is how I did it back then, and how I am doing my CJ5 now. Spray weld through primer on everything, including under/inside each hat channel, weld them on, then seam sealer, then primer, then undercoating on the bottom, then paint everything. I seal up any place water could enter the hat channels, no exceptions. I also seam sealer where every panel meets, no exception. After you weld anywhere, wire brush or sand the area and reapply primer if you can get to it.
You will need to buy a case of seam sealer, one or two tubes won't cut it. It's expensive, but 3M or equivalent is best, as the cheap stuff shrinks and can cause paint adhesion issues in my experience.

If you have already welded the hat channels and panels on without weld through primer, I would always set up to spray a rust encapsulator/primer/undercoating (like POR15) inside the channels and drizzle it in between where panels meet. I've done it both ways, and never had any rust issues. I also tried the above mentioned technique, then had the entire underside Rhino lined (rubberized bedliner). That thing was water tight, but if you ever needed to cut or weld anything under there that would be a nightmare. Lots of guys in my area like to bedliner the entire inside of the tub too. It's expensive, but there are a ton of benefits.

 

I'm leaning towards spraying all the parts with epoxy primer. Marking and cleaning spot weld areas to bare metal before spot welding . Get the whole thing together. Coat again with epoxy primer then high build primer. Undercoat inside of hat channels and seam seal seams that are under the jeep. Still want factory look above

 

I took a drill bit the size of the hole I made for spot weld. I cut drill bit off square on the end, put it in a drill and run it in the spot weld hole. It cleaned the metal but would not drill the metal.

 

There is a place here by me that will strip and E-coat your body for a price. I had my hood stripped and E-coated by them, it was not cheap but I wanted my hood coated inside because I could not paint inside the inside the braces. International Stripping is the company, they heat strip anything, that is not too expensive, but E-coat is a little pricy. They will strip a truck cab for about $400.00, it comes back looking like a new body.