Chlorine is a corrosive chemical, no matter what. The only thing that might withstand it, is powder coating. The easiest thing to remedy your problem is to remove the chlorine, or store your bike away from it. I doubt the metal of the engine is the only thing being damaged by the chlorine gas...
With regards to cleaning off the corrosion, I would suggest metal polish, but I would also recommend an Internet search on the topic of "cleaning corroded aluminum", or something to that effect. Depending on how deep the corrosion is, you may need to use #00 steel wool to remove/smooth it, then use #000 steel wool, to polish things back up -- follow the grain of the metal, though. After you finish polishing the fork tubes, hit them with a clear coat of paint, to protect them. Cheers!
1979 CB750K (sold, 2012, but not forgotten)
1983 Kawasaki 440 LTD Belt Drive (sold, 2011)
1993 Kawasaki Voyager XII