Decided to check my spare wheel yesterday, for the first time since I purchased the car about 3 years ago. Looks a bit worse for wear.
Much of the rust is surface; most worrying is the welded joints (didn't realise this is a two piece wheel) have rusted badly and there is corrosion around the stud holes. Tyre is unused and maintained pressure, but 22 years old now. Wheel and tyre are scrap I think?
Interestingly, the carrier frame paint and metal was near perfect when cleaned off with WD 40.
Car must now be over 10lbs lighter without the wheel. Not sure where to go next, but there is no way I would fit this wheel to the car.