Does anyone know if body seam sealer can be used on the exterior side as well as the interior side? Repairing rusted floors and two areas of worst rusting area above the formed brackets supporting the floor pans under the seat. Spot welds didn't seal panel and no factory seam sealer at exterior side so moisture got trapped and caused floor to rust through.
Would not have occurred if factory sealed seams from both sides.
Same kind of issue where floor pan laps with firewall.

Just wondering if there is some kind of issue with using seam sealer on exposed side of panel. Going to clean and paint underside as well.
Thanks

Good question, I've read a bit on another forum that guys were using seam sealer on their rear wheel wells after cutting tabs and folding them to open up their rears where the seams are. I was going to go to NAPA to get seam sealer this summer to do exactly that. I just assumed it worked for exterior use as long as it would be primed & undercoated.

Anyone else know?

Here is another seam sealer option:

SEM 1K Seam Sealer by SEM Products. Per manufacturer it is a single component professional automotive sealer for interior or exterior seams and voids. Comes in standard size caulk gun tubes, quarts and gallons. It remains flexible and may be painted within an hour. Can be applied to bare steel and aluminum or painted surfaces (but not acid based self etching primer). I paid about $20 a tube at an area automotive paint supplier but you can find it on line also. It is available in white, gray, beige and black. My limited experience with it has been good - it is easy to apply and can be worked with a tool or gloved finger with ease. The only consideration is that the sealer and surfaces it is applied to should be at least 70 deg F.

Other options might be Loctite polyurethane sealants with the PL or Pro Line identifier on the tube. You should be able to find these for less than $7 or $8 per standard caulk gun tube at some big box lumber and hardware stores. Two are identified for use on concrete and one as roof and gutter sealant. I have used these and like them but have not tried them on automotive applications. You can paint over them and they stay flexible. If someone has used these on a Jeep or other let us know how it went.

https://www.homedepot.com/p/Amerimax...5148/100011940 I just used this on my floors, but its for gutters so you could use it outside and I might go buy another tube to do so.

Yes it can be used on the exterior but I would also cover it with some like a under coat to help protect it

x2, both under and over seam sealer.

x's 3. I've done it this way several times.

My local automotive PPG store has 3M 08368 (white) urethane seam sealer for $20 and change per caulk tube. Almost half what Walmart, parts stores, and other sellers ask. It comes in other colors too.

That's good info. Probably a really good product, maybe the best way to go.

See the other seam sealer thread for the results.

just make sure ya get all that sealer off before welding...wow that stuff is flammable...they must have put the stuff on with a backhoe on my 1998 xj, must have been an inch thick in places...