Silver plated copper

The primary original reason to silver plate copper wire was corrosion resistance. Military, particularly aviation like silver plated copper..Plenty of Mil Spec Silver plated Teflon insulation wire for sale on eBay.                           
I have purchased plenty of it.
No special reason in audio use, particularly up against long grain OFC single crystal 99.999 etc copper.        
Silver plated copper is better for digital, computer and video in general.

Some folks like the sound of tinned copper... particularly for speaker cables.   
An aside.. I use Mil spec silver plated 12 gauge Teflon insulation wire in a quad twist, 30ft/33ft and a 39ft/43ft set for my system AC power. The fact is, the silver plated wire definitely reduces the bass some to my Magnepan 20.7 speakers. WHICH IS WHAT I WANT. Since I live in an apartment building for old people.(I am an old people) I was worried about buying the Magnepan 20.7 due to too much bass... But with some care I keep the bass tamed...           
In my experience with the long runs of silver plated copper the AC wire does affect and diminish the bass a bit. As I wrote this is exactly what I want...

I can mention the fact when a conductor silver, silver plate or copper is connected to a terminal of any sort..  IF the junction is sealed, the wire will not tarnish. If the junction is  somewhat protected from the air, (like in a plug but not sealed, it will tarnish slightly and take much longer to do so. If the connection is in 'open air' it will tarnish rapidly.Plus if you touched/rubbed bare copper strands with your bare hands, (like to twist the strands tight, etc)  it will tarnish even faster. 
And yes using a product like Caig Gold will lessen oxidation.  
For example, the silver plated wire inside AC plugs even after five years of use, had not tarnished. But the Same wire used for Magnepan 3.6 in the through hole back of the speaker, was very tarnished black in less than two years. (I am assuming the speaker vibrating was moving air back and forth through the open hole of the connector.