On Sun, 25 Apr 2021 20:17:16 +0100, newshound
wrote:
snip

I think the problem with that if there is significant corrosion in a
load-bearing region is that the flexing will break the resin to steel
bond and eventually corrosion will occur underneath.

It shouldn't should it (break the bond nor rust) as the fibreglass
would seal the outside and the foam the inside? I was thinking the
glass would be substantial enough (at the main stress points) to not
distort any more than the steel?

because I'd say your bike
mudguard brackets are not so highly stressed as some of the parts of the
barrow.

Well the bracket has to transfer (along with the axle) any difference
in loads / movement between the two fork legs (especially dynamic),
plus the fore-aft vibration and wind load of the mudguard itself.

That said, I am all in favour of repairing things. It all depends on the
location and extent of the corrosion..

Agreed, that's why I thought that doubling up (or maybe more) at all
the main stress / weak points.

I was thinking we end up with a fairly substantial (where it matters)
fibreglass tube frame, even if the steel was to rot away inside. ;-)

Cheers, T i m