Well two component spray foam will cure well in enclosed spaces, you can actually buy closed cell, two component, that you can mix and pour that is used for filling cavities in boats for that purpose.
ordinary spray foam can work well as well a long as you apply it in layers so it has time and humidity to harden.
Not sure about corrosion , would not know why except that with moisture entering the space you have lot the ventilation so it will stay wet and as a result enable rut to develop faster.
Later j
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