What you missed twit, is that the silver is not contributory to the corrosion. That copper is sacrificial to silver, and that the cause is air/water getting to the copper due to cracks/failure in the plating.

Again, this process is well understood and often exploited by jewelers and metalsmiths. It's a big world out there, jackass - try learning something.

Peter Wieck
Melrose Park, PA