Working on a bike that has had significant indoor turbo usage, (i.e. a lot of sweat has run down the headset) and corrosion has bonded the aluminium spacers to the carbon steerer. The steering is stiff and notchy such that the bearings must be replaced, but the spacers are well and truly stuck in place.
I have tried getting some boiling water on the spacers, wrapping a boiled cloth on there, I spent a few hours dripping lemon juice down the gap (I think I read that on Park Tool), I've tried WD40 and have tried turning the top spacer with slip joint pliers (water pump pliers) as hard as I can, but no progress.
I will not want bang on the top of the carbon steerer any harder and the alu piece on top is proud because the bung is seized in place also (still functional). My experience and exploratory taps say that no amount of hitting on top will free this headset up.
How can I remove these very stuck spacers without damaging the frame or fork? I'm hoping for a proven answer because if I continue but damage the spacers further without getting them removed then I potentially make the bike unsafe and so unrideable.
Update: I am still looking for an answer. Nothing forthcoming just yet. I'm thinking that somehow cutting through just the spacers, maybe with a rotary tool, would do the trick, a-la DavidW's answer in the first comment. Maybe cutting not quite all the way through and then forcing the ends apart to pry them off. I asked in my trusted local shop at the time and they said they would do something similar but were too busy to take it on.