Utilizing Expandable Foam

[Mstg007]

https://www.youtube.com/watch?v=hf2uecgDLrs

 

I wanted to get your ideas on this approach to doing "rough" body work.

 

My understanding is to cut out all the rust and sand it down. Spray the rustoleum to prevent future rust. Then Spray the expandable foam. Once the foam drys, cut it down to match the body surface. Apply Bondo, sand then spray.

 

 

[primergray]

https://www.youtube.com/watch?v=hf2uecgDLrs

 

I wanted to get your ideas on this approach to doing "rough" body work.

 

My understanding is to cut out all the rust and sand it down. Spray the rustoleum to prevent future rust. Then Spray the expandable foam. Once the foam drys, cut it down to match the body surface. Apply Bondo, sand then spray.

 

 

I'd be worried as hell that the foam would hold moisture in there and you'd end up with way worse of a problem than you had before...

[digitaloutsider]

 

Sometimes I literally can not.  This is one of those times.

 

Expanding foam is not an appropriate way to repair your car.  The ONLY way I could EVER see doing this is if you need an absolute jalopy to get through inspection so you can drive it another few months before you get something new.

[White93z34]

Depends what your end goal is. 

 

Restore a car to decent condition

 

or 

 

Get a beater down the road awhile longer

[primergray]

Hell, just use POR-15 and fiberglass mat for a patch instead...

[Imp558]

Foam = sponge = moisture retention = rust = dead car.

[Calvinator]

I've done it many times on my Jeeps and Monte Carlo rocker panels.  Results will be great to excellent, but these are just everyday driver cars at my home.  And of course, only used for cosmetic pieces, nothing structural.

 

Rust is sandblasted away.

I use polyurethane type of foam, it is water proof when dry. 

After foam is dry and trimmed to shape, I use Duraglas filler for bonding and strength.  Strong and waterproof!

After Duraglas, any body filler topoat.  I don't use bondo, personal preference.

Sand.

Prime & paint.

[RobertISaar]

closed-cell foam won't absorb/retain moisture, but this is as domestic as it gets.

[94 olds vert]

If the car is a beater, I don't see the issue with it. I have seen a lot of people fill it rust holes with spray foam around here, then paint over it. Honestly, it doesn't look too bad. Looks like a really bad bondo job if anything. 

[Imp558]

For the record, Bondo Gold is great as a skim coat. It's very fine and smooth, I skim coat after I do a repair. Nothing beats flanging the hole and putting a new piece of metal in except replacing the whole body panel. Doing a repair with steel isn't any more expensive than bondo but you do have to cut ALL the rust out either way and if it's new steel it needs cleaned to remove the oily film from it. Edit: steel rivets, not aluminum.

Edited May 24, 2017 by Imp558