Spray in foam insulation

[kieth]

just to update this issue, I decided not to put foam of anytype in the cab of my truck. I am spraying undercoating in the cavities for noise and rust issues. Kieth

[Frizzle Fry]

Just for anyone doubting the rustification effect of the spray foam, I have first hand long-term experience with it:

15 years ago when I was a (dumb) teenager I had the bright idea to put that stuff in the roof of our rust free California 64. I put it in through the visor mount and dome light holes.

Today the truck still has solid OG rockers cab corners etc. Guess where the ONLY rot is on the truck? Yep in the roof just above the windshield. Why do I see 100 other trucks with worse lower rust than mine but none in the areas I have it? Could only be one thing...

[daverod]

I don't get it. Were does the water come from? If you have a space and you fill it up with foam I don't think there is any air movement? Water can't pass though metal. The air that's in the space to begin with is pushed out. I'm not saying it doe'nt cause rust but I don't really see how. Where are all the people with master degrees and PHD's. I did a search "Does spray foam soak up water?" It would seem that most would say no? Most = foam companies. Did another search Does spray foam cause rust? Same deal all the foam companies say no. It's almost like dealing with politicians.

[Frizzle Fry]

I bet one of the factors may be the expansion/contraction of sheetmetal as a result of thermal cycling. This may cause the metal and foam to separate enough to allow water to wick in. Once it's in there the lack of airflow causes it to remain there longer than it would otherwise. That's my guess...

[monolith]

If you want to see a spray foam horror story, click the suburban link in my signature, though I certainly don't know if it's the sole culprit or even the accelerator of the rot, but there's a ton of rust, and a ton of cheap spray foam, I suspect the two have at least something to do with each other.

Some speculation on how the moisture gets up there: When the driver's out in the weather he/she gets wet, jumps in the cab and turns on the heater. The warm moist air rises, steams through the screw holes, cab light hole and sun visor holes. Or maybe just turning on the heater in the cab in the winter and the air in the summer causes the water in the air space to condense. I don't have a clue, but the discussion has intrigued me.

[kieth]

Condensation from the hot cold cycle, it drops out between the foam and the roof skin because of the temp difference.....it gets trapped there and rust starts and keeps going. Refrigerated trailers life cycle is governed by this problem, as they age the trailer gets heavier and heavier because the foam collects so much water. The sidewalls are aluminum so they do not rust, but the fasteners are not so they rust out, the trailer gets "cancer" and its life is over. Now it is only good for a cheap storage trailer not a refrigerated trailer anymore.

[daverod]

Found more stuff and stuff . http://www.greenadvantageinsulation.com/faq/

[Paulie]

dude never put that stuff on a car/truck just causes problems i have never seen anything good from it ever I just got done cutting away rusted rockers and cab corners all foam bad bad

[daverod]

I think a lot of times the rust or hole is already there and people just spray it on there to as a quick fix. I'm not sure that it's the cause? From everything I've read ( from the foam people) they say it doe'snt cause rust. On the other hand there's a lot of truck people that say it does.
I've also found out that they use it when installing sound systems. They spray it to deaden the sound. When I was reading that stuff nobody said anything about rust or the foam soaking up water? I don't really think it soaks up water. I've seen it used in boats. So far as it causing rust I don't really know what to think.http://forum.camarov6.com/showthread.php?t=81506