Protecting copper from cast iron

My plumber ran some supply lines in a very narrow brick channel next to the cast iron waste stack. Unfortunately, the copper and cast iron are touching at points, and the channel is so narrow that it's not possible to get any foam insulation in there. What else can I use to protect the copper from corrosion? I obviously want something that will last a long time. I was thinking of putting some vinyl PVC wrap tape between the CI and the Copper. Will that work? Other suggestions?

They in fact do make a plastic wrap for copper pipe. The stuff I use says UPC tape. I don't know what they sell in IPC country. But yes, you can throw some tape on the pipe.

Good to know. I can't seem to find the stuff online anywhere, though. This is the closest I've come across:
http://www.northtowncompany.com/polyc.html
Any other keywords you can suggest? I am under UPC, so maybe I can just call my local plumbing supply store and they'll have what you describe.

You could go to a craft or hobby shop and buy some sheet styrene. Cut some strips, slob some glue on and shove it in. It should never move, rot or rust. You could also go the the meet counter and buy a steak and use that thin styrofoam thing that they come packaged in. While your steak is cooking on the grill, wash it, cut it , glue it , and stick it between the pipes then go eat your steak.

There is going to be very little, if any, movement so it makes little difference what you use to separate the pipes. Duct tape, cardboard, or any kind of plastic tape is sufficient.