Chas, the PC boards are all coated to protect them from corrosion, something that has been done on micro-electronics for two decades or more. The reason behind this is the extremely low voltages and currents that these systems operate on, thus the slightest amount of moisture would provide a conductive track that could trash the system. I think the only thing that could corrode would be the solder joints, but now these are pure tin, so they shouldn't corrode either. Lead was eliminated from solder a decade ago (EPA requirement).

A lot of the micro-switches are hermetically sealed, so no chance of corrosion on them, and one of our dearly departed members, HankB, had a Yamaha PSR-2000 that he frequently joked had a drinking problem. Someone dumped two gin and tonics in the keyboard one night while he was playing. You would have thought this would have destroyed the keyboard. He turned off the keyboard, dumped out the liquid, then opened it up and dried it with a hair dryer. It's still working to this day, and that was nearly 20 years ago.

Now, I do my best to keep everything bone dry, and while living aboard the sailboat, I ran the AC every night when I came back from playing an outdoor job. I left the gear in the cases, but kept the cases open for at least 8 hours in the AC. However, it only took about 20 minutes in the AC for the outer shell of the keyboard to be bone dry.

All the best,

Gary