My M85 fork tubes are rusted a little where the taper meets the top fork clamp. Can grease or something similar be applied to the taper during reassembly to slow down the corrosion process? or would this make the forks move? Thanks!!

Treat the tapered section of the fork tubes with phosphoric acid following the instructions on the bottle. It may be called rust converter where you live.

That will cause all corrosion activity of the steel to stop, and create a protective layer on the steel. The process must be complete before assembling (to avoid damaging the aluminium top clamp with the acid)

Assemble the taper dry and clean (no grease).