Experimenting with expanding construction foam.... 
Nick's theory aside dare we ask why, how etc?
We have hollow steel balustrades and gates all around the house... They rust like fuck, partly I suppose because the original steel was crap and partly because they were never sealed properly (in some places I have had to drill holes and let the water out)... So they need painting all the time...
Last year I tried an experiment of drilling holes in two gates and filling them with the expanding foam. It does go everywhere and I ended up looking like the bloke in Nick's picture but it seems to have done the trick... No more rust...
So today the gate posts on the driveway get the same treatment!
