Has anyone had a proble with corrosion & spray foam

[elkhunter338]

Back about 6 years ago before I found Iboats I replaced the floor in my Cheiftain. I used marine plywood and stainless steel screws to secure the floor and coated it with skid not deck coating. All is working very well.
However since then I found this starcraft site and had a thought.
When I put my floor back on I reused the old foam (in good shape) I also added some white board foam from Homedepot and I also used some spray foam from homedepot to basically glue the foam to the bottom of the boat.

My concern is with the spray foam stuck to the boat, and bilge water has anyone had this start to corrode the boat from the inside?

If I had to redo my project over again I would have used glove-it on the whole inside of the boat, but I had not found Iboats and the starcraft guys until long after my project was completed.

 

[North Beach]

Re: Has anyone had a proble with corrosion & spray foam

EH, several of us have removed sprayed in urethane foam from our boats and found a lot of corrosion. I'm not real sure the foam is causing it, but would never personally go back with the foam.

FWIW, we've also found corrosion on the transom skin and we all know there's no foam there. It would be nice if someone could figure out the exact culprit.

 

[reelfishin]

Re: Has anyone had a proble with corrosion & spray foam

I would think that the only reason there would be corrosion is due to the foam or wood holding salt deposits over time right against the aluminum?
Could the foam be wearing against the oxide layer in the aluminum exposing it to corrosion?

I had a smaller aluminum trihull, brand unknown, which had it's lower hull filled with small foam pellets, which inturn were soaked after years in the elements and saltwater. The hull was badly pitted where the foam laid and held saltwater. The same where the wood touched the transom. The worst parts were where the foam was wet and really saturated. It was so bad that I scrapped that boat.
There were no non aluminum fasteners or anything I could see which would cause electrolysis. I've been told over and over again by engineers that aluminum does not corrode with saltwater, if that's so, there must be something reactive in either wood or foam which causes pitting.

I've got a row boat, with a wood panel inside the transom, no floors, no SS hardware, the outside of the transom also has a 3/8" plywood panel under the motor. It's never had a motor on it, just oars. I replaced the wood this past spring, the aluminum under the wood was all white with corrosion. It's never seen any electricity, and has never had a motor on it. The bolts which held the wood in place were all aluminum. Even the oar locks are white pot metal or aluminum. If aluminum doesn't corrode in saltwater, then what makes all that white powdery mess? The wood appeared to be plain plywood, not PT.

 

[elkhunter338]

Re: Has anyone had a proble with corrosion & spray foam

thanks for the input, that is kind of what I thought but I really do not want to pull the floor up and look. I wish I would have never tried to keep the foam under the floor and of course never used spray foam below the deck.
I think what I am going to start doing is adding about 10 gallons of fresh water and lemon dawn soap in the bilge after I take the boat out of the salt water. I only use for a 2-10 day time in the water. On the way home the soapy water can clean the salt out of the bilge, drain when I get home and call it good. Hopefully my hull will last for many many years.

I too have found alum turns white, I think this is where salt gets between two surfaces and eats the alum up. I have had places on the alum railing get holes in the alum where an alum clamp was clamped to the railing, the salt got in there and did its work. Nothing lasts in salt water for ever.
Welded boats are better since there are fewer places where two pieces of alum are touching and where water gets in there.

 

[North Beach]

Re: Has anyone had a proble with corrosion & spray foam

I think you folks may just be right. My mariner was from the bay and it was ate up with the skin cancer everywhere there was foam.

 

[Pugetsound]

Re: Has anyone had a proble with corrosion & spray foam

Very likley a foam reaction to the salt air and water. Whidh transfers to the Aluminum. I kno the salt enviroment will effect the Aluminum its self. I every month would loosen the deck screws and rinse the areas real well then a little sealer and tightn them again, when I was in the Salt water a lot.