Ipod, Galaxy tab charger cables stop working?

Factual Questions
1

I have now had two charger cables, one for an Ipod Touch and one for a Samsung Galaxy Tab stop working. Both are the similar looking connection like the Ipod, both have what looks like verdigris? on some of the contacts inside.

It looks like blue corrosion :confused: Attempting to clean it off with rubbing alcohol has not worked.

What the heck is this?

2

The contacts are either plated copper or brass (a copper alloy.) so if it has greenish-blue crap on it, then something is getting in there and corroding them. Are they exposed to salt air, or do you carry them in a way where they’re exposed to sweat?