Antibarrier tape / stickyback

[jmc4sail]

Several years ago Brian did a lot of work on our rigging and used what I will call an anticorrosion sticky-back product to stop/inhibit electrolysis from occurring between 2 different metals such as a stainsteal mast fitting and an aluminum mast. I was also given a 4" wide strip which I am now out of and cannot seem to find anywhere. Can anyone tell me what that tape/sticky-back is called and/or where to find it? Thanks in advance, John