In some other threads, I've seen questions or suggestions about using electrolysis to clean horns. Right off the bat, let me say I'm not endorsing that idea, especially for instruments. OK? But since it's obvious that there's some question as to whether the trumpet should be the anode or the cathode, and the like, I'd like to share a link which I found most helpful when I put together my setup for cleaning old tools some years back.
ELECTROLYTIC RUST REMOVAL (ELECTROLYSIS)
He offers a link to another site on conserving underwater archaeology. There is a vast store of solid information there, especially in the silver and cupreous metals files. I should add that for me, electrolysis is the last choice. It really leaves a nasty-looking surface, so I prefer a bronze-bristled wheel in a grinder, or weak acid (citric, with acetic as an alternative), or just a series of abrasive rubber blocks and a wire brush. None of that applies to trumpet cleaning, just giving a perspective.
All I hope to do with this posting is to clear up some of the misunderstandings about the process. Don't ever think that I believe this technique should be used on a trumpet.