I have a $300 MTB used for commuting. It has been three years now, and the rain and snow have said their word. Two weeks ago I disassembled the fork and spent a good one hour with the sandpaper, removing rust. Still some was left. It has been two rainshowers from then. Yesterday I had another look and ... it is not promising.
I have move aggressive means of removing material (so that there will remain no rust) - a grinding wheel. However, I am afraid to use it, as I guess it will be weakening the tubes too much. I do not seek top performance - it is a no-steal bike (for example the handlebar is visibly bent).
Below are the two pictures. Should I clean the rust? How? How reliable is the fork currently? How long does it have left?