my solution:

Take a bigger tub or bucket, and fill it with vinegar and another with water. Drop the copper in the vinegar and wait 2-24 hours depending on how bad it is, then drop in the rinse water and let dry.

This will remove the corrosion and brighten it back from #2 to #1 copper. It isnt really expensive to do and if you have alot of wieght can made you some extra money for a a couple dollars and few minutes of your time. If you are trying to do under 25-50lbs, it will not pay off well as you have more invested than you make back. after all in most areas it is only a 10-25 cent difference.