The Stovebolt Site Forums The Shop Area Paint and Body Shop Drip edge seam sealing. Before primer, or after?

So, I'm getting closer to primer everyday on my panel truck. I know I want seam sealer in the "eavestrough" that runs the length of the body, and over the rear doors. I also want to use it right under the drip edge-eavestrough too, as I have a little valley there. My truck has windows on the sides of it, I don't know if regular panels have this valley, or gap right under the drip edge or not, as I've never seen another one in real life.

I bought paintable seam sealer, but I don't know if I should put it on over the primer, or put it on under the primer. I can see a case for either really.

What's SOP on this?

Thanks.

I usually clean the metal after sanding or grinding it then apply the seam sealer then primer.

Most vehicles you see from the 60's and older will typically show a cracking and separation of the seam sealer to the drip rails. To offer better protection in case this happens in the future, I would recommend a good epoxy primer throughout the drip rails/seam areas (including the undersides you spoke of). Once cured, a light scuff/prep as if you are getting ready for any other paint product, then apply the seam sealer. It tends to set up rather quickly, so a quick dip of your finger in some pre-clean and drag along the surface, it will normally smooth out any imperfections. Additionally, any exposed areas you may see (as in the undersides of the drip rails) you may get a nicer looking job by taping off about 1/8" (more or less) from the seam. Be sure to pull the tape up before it sets too well.

Epoxy primer? Hahahaha. I'm using red oxide. Maybe I'll put the seam sealer between coats of primer.

All of the 3m sealers that I've seen say you can use them over paint, primer or bare metal. If you use the factory as an example it was squirted in to the bare metal before the bodies ever got to the paint line.

Denny Graham
Sandwich, IL

I like the idea of seam sealer on top of a epoxy primer. I've seen too many seam sealers on to of bare metal let go after years go by, only to see rust under them because they were over bare metal.

I would think the epoxy primer would seal the metal preventing that, should the sealer let go.

Dan

I agree with everybody that said to epoxy prime 1st, then apply the seam sealer. However I've used a 3M product called "Drip Check" to seal the rail gutters. It's thinner in consistency than regular type seam sealer, and can be applied to bare clean metal and then urethane primer over it. It flows out real nice and you can smooth it with your finger if required. I used that on my '54 Chevy Panel truck 14 years ago with no signs of cracking or rust thru. But in current practice everybody suggests epoxy prime 1st, then do all your body filler, seam sealer etc on top of the epoxy.