Originally Posted by DannoXYZ
It's not that bad. Sand the seatpost lightly with oil and wet-n-dry sandpaper, 600-grit should even out that corrosion. On the seattube of the bike, spray some WD40 down there and run a
brake-cylinder hone through for about 10-20 seconds:
Wipe everything off with clean rags. Re-grease seatpost and re-install.
whoa. really dumb idea. Danno, I wish you would stop making thes types of suggestions without knowing what you are talking about.
You want to remove only the corrosion, not ream out the tube, that will weaken the tube and make proper seatpost fit impossible, ruining the frame.
LIGHT abrasive to remove any rust, then you can try a light coat of clear laquer to seal, make sure it dries for days, then a new seatpost with lots of grease.