Question... is the corroding Thruxton parked outside 24/7 or is it stored at night in a dry garage? Makes a big difference. If you store it outdoors, a good waterproof but breathable cover is a necessity.
Also, if you live near the ocean, the salt air pretty much eats away at anything metallic whether it's indoors, outdoors, covered, or not!
If you ride home in the rain, it's good to wipe her down or blow the water off before putting it in the garage.
Ever heard the term "rode hard and put away wet?" hehehe... Here's a neat little blower tool for that:
http://www.carguygarage.com/comodr.html
A little WD-40 sprayed or applied with a rag and wiped onto the areas in question will also displace water mist and keep the air from oxidizing it, whether it's plated steel or aluminum. (Just keep it off the paint and tires if you can) Carnauba wax on the paint will keep the moist air away from the paint and the water will bead up so you can just blow it off.
Sorry your having the corrosion issues, but some tedious, regular polishing, drying, and waxing will at least slow it down anyway!
You probably know all this anyway, but it's still good to bring this stuff up again for all the newbies that join the forum daily.
Cheers,
BLIGHT