I am a sheet-metal dilettante and would be grateful for some general thoughts on seam sealers, or a good link or two describing types, brands and use thereof?

For instance, commenting on a photograph shown on a different thread, sean_V8_914 wrote:

"...is that the Wurth seam sealer? I really like it for the floor junction but use SEM self leveling on teh (sic) top seams"

That's over my head. "self-leveling?" I used some on my bathroom floor tile project last month, ha, ha. But, the idea makes sense. What is it?

I have a few different contraptions (old vehicles) and a miller mig so I feel like I can do rust-repair...but, hundreds of members of this board actually know what they are doing and do it well. I want to too!

I know seam sealer is important and generally use something (roofing tar?, silly putty?), but I don't have a criteria (clue) about what, when, or where to use the various types I see at the auto body/paint store.

BTW, I forgot to do a search on this topic. If something is already out there, let me know by posting a humiliating "emoticon."

I have been using 3M seam Sealer for years. Its easy to find, buy it in cases and run huge beads with a caulk gun. Then spread it over the seams and let dry. Its white, so you can paint as necessary.

That's logical and helpful, thanks Brett. My general observation with 3M is when I go to buy it they will have seven different versions? Does it matter?

I've read about the advantages of SEM 2 part seam sealer, that it is runny so it will go down in the seam better, though I can see that could be a problem, say, between the long and floor.

The "Paint Store" it's called by me has a display with a bunch of different ones all squeezed out in lines, they must have 10 types.

That explains the "self leveling." awesome, thanks, 2xNathan!

Where is the Paint Store you referred to ?

SEM makes a few different seam sealers. I really like the SEM products. IMHO the two part products are better than the one part. Part of the problem though with the SEM stuff, is you must have the right applicator gun and the mixing nozzles, they don't use a regular caulking gun.

what exactly is the purpose of the seam seeler anyway. After finally getting it all out of my car, I just painted it and never put it back.


Be gentle

It's actually called "The Paint Store". I got them to order me PPG stuff.
http://www.ocpaintstore.com/

I bought a seam sealer from Eastwoods and have had really good luck with their product.

I hate the stuff myself because I have found rust UNDER it many times. The theory should be that it is more flexible than paint so it won't crack, whereas paint could crack and allow moisture in. But I figure if there is enough flex to crack paint, I want to weld the seam and possibly add bracing to stop the flex. Then the paint will keep moisture out and not potentially trap it like sealer. I think I'm in the minority though.

Thanks for the explination.

The problems with our cars is there is already rust in the bodies, so unless seam sealer is applied to bare steel or e-coated steel you will run the likelyhood of getting rust under it. Seam sealer is essential for a modern street car. Many times the factory applications of seam sealer actually caused more harm than good. Go look over some new cars and see how the seam sealer is installed. We have learned a lot about rust and corrosion protection in the last 30 years.

I bet galvanized steel bodies did more to stave off rust more then better seam sealer. I'm not saying that there have not been advances, just that a better substrate need better seam sealer less.

the prep work under it is far more important than the actual product.
the products I use are based on my own weather testing. some junctions are designed to flex so a flexible sealer is required. some areas will see moisture trickle down in there no matter how fair weathered teh car is so a sealer that flows out makes sense there. if you seal in some rust or moisture due to poor prep, don't blame the product when it fails. Scotty B talks about the importance of cure times. prep work has gestation periods to observe also, especially corrosion treatments, neutralizers and dry times. some sealers leave a bead, some flow out flat, some are rubbery, some are paintable, some have rust passivation agent built in, some require a specific base under it, some work better on bare steel

this subject is so closely linked to prep work and where it goes that a more direct answer is tough to give when your a ramblin babbler like me

exactly what I was hoping for. now I know a lot more than i did.