I just received mine so I have not had a chance to see any reaction. I am going to assume that they will corrode unless sealed. I sealed up the lid with a couple of wraps of teflon tape-that white stuff they use to seal water pipe. It is available in any hardware section of K-Mart, Walmart, etc.
I am not sure about teflon paint. We use another liquid threadsealer called "Liquid Teflon". It is a loctite product # 56747. You might be able to smear it on the inside of the cap in the same way you could daub paint, but I'd be worried that it might be toxic.
Give the teflon tape a try. I have one vial that had been sealed up with it for about a year with no visible corrosion. It's cheap too-about .89 for a 25 foot roll.
Regards, Vince