Effect Difference between Bondo and Seam Sealer
 

I just finished replacing my floor board and welded it pretty good but its' kind of ugly. Anyway, can anyone explain what the different effect I would get using seam sealer or bondo, inside and outside the seams of my floor board, in terms of:

Rust
Weather
cosmetically - I want it to look decent.
Can either one be placed over Zero Rust?
I assume seam sealer is paintable.

I'll take a shot at some of your questions.

Many different products are labeled seam sealer. Some are paintable and almost like silicone caulk. Some are no more than tar based product.

Good seam sealers block out all moisture, whether painted or not, and keep rust from crawling out of seams you just cleaned. Unpainted bondo draws moistiure like a sponge, and can cause rust to return even worse than it was before.

Bondo sands nicely, most seam sealers can be razor blade trimmed and thats about it.

Good seam sealer will stick to about any clean and dry surface, use it over primer sealer for extra protection.

I've never used ZR, but seam sealer should stick to anything that primer will.

One other benefit of most seam sealers is that they are flexible and used in places where 'flex' is likely to happen such as between two tack welded panels. A bondo, as 'fenders mentioned, would be more sandable and paintable, but also would be more prone to crack, creating a place to moisture to attack a seam.

I would put a "plastic filler" (fancy term for bondo) on the visual parts of the floor so that it could be finished off nicely, and seam sealer underneath the new floor welds.

If you've never seen seam sealer, look under the hood of your regular car. Look at where the apron meets that strut tower. The caulking type material is the seam sealer. All newer vehicles have a ton of seam sealer around the entire vehicle where different structural body parts are joined.

Ilya

Ok. I'm clear on Seam Sealer, but I was watching this video and the guy first put on some filler then a bondo type product over that. I assumed they were the same.

Does filler absorb moisture like bondo type products.

Even in the auto stores, there are Bondo products and body filler products. So what is the main difference between the two????

I may be wrong but I always thought that bondo products and body filler was one in the same, just different companies.

There are specialty products available that can be used as skim coats over bondo to cover sanding scratches and pin holes in the bondo before priming but they basically are just thinned down body filler. Most body fillers will absorb water, however there are water resistant fillers available and are preferred in areas where you cannot get to the back side to seal a damaged area such as in the rocker panel of a car.

Most seam sealers are waterproof and will not absorb water but over time they can let go and allow water to get under them.

IIRC, Bondo was the original product. Then others followed. I try to stay away from Bondo for body work. I've had good results with a product called Eurocoat or Eurosoft (can't remember the exact name). I usually cover this filler with a putty made by the same company. The putty fills the tiny scratches left in the filler from sanding. Then a good coat of filler primer and sanding, priming again.

Ilya

51PanelMan - You are probably talking about "Evercoat". I used their "Extreme Rage" filler and "Easy Sand" Glazing putty. Great stuff.

Just picked up a tube of 3M seam sealer at O'Reilly's, it's not cheap so it must be good, about $15 for a caulk gun sized tube. It does say remains flexible but is also paintable when dry. I plan on using it on the inside of my fenders after weld in patches and priming are complete, and probably coat the whole underside with truck bed liner.

Scott