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.
Great idea! When I wrenched at a bike shop, we used an adjustable reamer, but the hone looks like a winner.