Sprayfoam shipping container

bazbrady

Hi so im thinking of sprayfoaming a 20 foot container i have,need to store items in it and dont want any condensation,has anybody done it here,does it work but more important does it cause issues with the steel underneath the foam,i cant see how as its fully sealed and basically airtight so moisture would be only on the outside skin,right?...

CJhaughey

bazbrady wrote: »

Hi so im thinking of sprayfoaming a 20 foot container i have,need to store items in it and dont want any condensation,has anybody done it here,does it work but more important does it cause issues with the steel underneath the foam,i cant see how as its fully sealed and basically airtight so moisture would be only on the outside skin,right?...

No, polyurethane foam needs moisture to cure, there will be a degree of moisture under the foam and this will react with the steel over time to cause rust.
Spray foam is also not watertight, water will find its way through the foam over time.
Condensation forms on the cold side of an insulated surface.
To help prevent condensation you need to lower the humidity inside the container through removal by a dehumidifier.

looksee

I have household stuff stored in a container and so far it is doing fine. I did have a couple of those small throwaway dehumidifiers in it but they are now ready for replacement and I haven't been able to find any (decent) ones.

Lumen

CJhaughey wrote: »

No, polyurethane foam needs moisture to cure, there will be a degree of moisture under the foam and this will react with the steel over time to cause rust.
Spray foam is also not watertight, water will find its way through the foam over time.
Condensation forms on the cold side of an insulated surface.
To help prevent condensation you need to lower the humidity inside the container through removal by a dehumidifier.

I'm not sure that's exactly true.

Condensation forms on the cold side of impermeable insulation where there is a route for warm, moist air to reach that surface.

If the foam is open cell PU, condensation will form inside the insulation at the dew point, not on the back surface in contact with the steel.

CJhaughey

Lumen wrote: »

I'm not sure that's exactly true.

Condensation forms on the cold side of impermeable insulation where there is a route for warm, moist air to reach that surface.

If the foam is open cell PU, condensation will form inside the insulation at the dew point, not on the back surface in contact with the steel.

If there was no moisture present at all when the foam was applied then your theory may be true but any water in the atmosphere will be present at the surface once the foam is applied and trapped by the foam.

Lumen

CJhaughey wrote: »

If there was no moisture present at all when the foam was applied then your theory may be true but any water in the atmosphere will be present at the surface once the foam is applied and trapped by the foam.

Steel doesn't rust with exposure to water alone, it rusts with exposure to oxygen. If the water was truly trapped then there would be no significant rusting as that oxygen dissolved in the water would soon be used up, and if the water was not trapped it would evaporate.

Either way I don't see how steel insulated with open cell foam is going to rust.

But if you're bothered, just seal the steel with paint or lacquer first.

PU foam core steel composite panels are a thing.

CJhaughey

Lumen wrote: »

Steel doesn't rust with exposure to water alone, it rusts with exposure to oxygen. If the water was truly trapped then there would be no significant rusting as that oxygen dissolved in the water would soon be used up, and if the water was not trapped it would evaporate.

Either way I don't see how steel insulated with open cell foam is going to rust.

But if you're bothered, just seal the steel with paint or lacquer first.

PU foam core steel composite panels are a thing.

I am only going by what I have seen, its not conjecture on my part.
Steel behind PU foam will rust, it may be different for a factory made panel where they are made in temp and humidity controlled environments with steel that has been coated already, if you think that's the same as spraying foam from a tin onto a used 20ft shipping container then I would say its not.

gctest50

How do reefers manage ?

CJhaughey

They are factory made and the insulation is part of the container not sprayed on the outside.