Cleaning supers

[Jon]

I routinely fumigate old comb with 80% acetic acid.
I would be really wary of taking old comb from another beekeeper.

Bees will draw fresh comb very quickly from a starter strip at the right time of year.

I was at a presentation on AFB by Robert Paxton last Saturday and he pointed out that scorching equipment does not get rid of 100% of spores.
Having said that, I think the main risk is from old comb, especially old comb which has previously had brood reared in it.
He pointed out that AFB spores can be viable for up to 45 years so equipment sitting in the back of a barn for decades can still be a risk. The spores are highly tolerant of both heat and cold.

Bear in mind as well that brand new bee equipment is not that expensive. A Thorne seconds flatpack super is £12 and a broodbox is £18.
A lot of old beehives are best used as garden ornaments or getting a bonfire going.
A lot of them seem to be home made and do not always respect beespace. A couple of mm can make a lot of difference re the amount of brace comb and propolis produced.
Worse still, if the frames are a bit tight they can be next to impossible to remove.
I remember spending half an hour getting the first frame out of someone's hive which was a couple of mm too narrow.