Automotive seam sealers and primer/sealers....what, where, and how?

I have not one clue about seam sealers, really, but I am going to ***-u-me that I would want them over any welds that aren't covered with bondo (like the exterior repairs)?

Mostly around the riser I had to cut up and replace the bottom half of, and all the spot welds joining the floor to the body sides underneath? And where its welded to the riser for that matter?

I plan on herculining or similar the whole underneath and in the wheel wells, so that would also cover all the seams.

And for the interior, would I want sealer along the floor panels where its joined to the sides?

-------------Now, that was the caulking/brush on stuff, next is the spray on type------------

Finally, are sealers and primers pretty much the same, or is there a big difference and its pretty important what to use?

All my vehicles I painted have been rustoleum spray bombs so this "real" painting thing is new to me. Even tho painting101.com has some good info, I'm still unsure about the "base"

Thanks for any help/advice!!

 

this is what I used for sealing all seams .all inside of tub. edge of floors , fender wells inside edge . and the most important area the cowl seam under windshield
3M brand Brushable Seam Sealer part# 08656

 

a primer is the coat that sticks to the substrate(body or frame, plastic or metal) to promote paint adhesion, the sealer stops the undercoat(primer) from bleeding or settling under the finish(paint) imho any paint product that air dries (non catalyzed) like lacquer is a waste of effort I dont use any products that are not activated and have 10 to 15 year old repaints that still look good.

 

Seam sealer goes over seams. This keeps water from flowing between the panels. First you must paint primer over the metal. Then seam seal the seams only. Then apply the top coat.

 

So prime, seam-seal, paint, or seal-prime , then paint?

 

Buy a quality "paintable" seam sealer. Read and follow label directions.
I always prime first.

 

Just did this myself...prime, seal, prime, paint, clear.

I used the brushable type on many seams, in particular on the underside of the body. Any seams that were meant to be "neat" I used the type that comes in a caulk gun so I could lay down a nice bead.

 

3M has an entire page of sealers http://3mcollision.com/catalogsearch/result/index/?aad_search_result=1319&q=Seam+Sealer

Each of these products will have some kind of instructions, a MSDS, and possibly some brochure/documentation.

Note that a lot of cars use a semi-solid seam sealer to fill the beads between panels.

Don't use a sealer between bolt-together fenders and brackets and stuff. Instead use strip caulk (Moretite) that does not harden.

 

Thanks for all the advice everybody!!