Vauxhall experimented with filling the A, B etc pillars with expanding foam to add crash strength was back in the viva days
This came up recently on here about using expanding foam to prevent rust. many have said that it just absorbs water and promotes rust. Personally I am not sure, so test. Cleaned and abraded plate, 2 dobs of Everbuild fire rated foam in fetching pink. One cut one left sealed. Left outside on my boat next to the sea....
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Will see what's underneath in a while..
Might try some box section if I can find some handy...
When I worked in a lab, many moons ago, one of my jobs was calculating the moisture content of materials being delivered by suppliers as it was an old trick to hose the load down to create more weight and therefore charge more. I used to weigh a sample then put into a vacuum chamber for a few hours and weigh again.It’s an open cell foam.
We had some closed cell foam around a vessel a good few years back and wasn’t supposed to absorb water but did. We weighed it and then heated it up, water got in but steam didn’t get out and eventually exploded, didn’t expect that.