I've used electrolytic to derust some tools and lathe parts. I didn't seem to have any effect on unrusted surfaces, but I didn't measure anything either.

From what I have read, it only converts the rust at the molecular level by liberating the oxygen from the FE02 and doesn't hurt good surfaces. All that's left is basically the pure iron that was converted to rust in the first place. It gets left behind as an ultra fine black powder. This needs to be rinsed off pretty quick, since it sticks pretty good after it dries.

I think you will be OK with the machined surfaces, but they may discolor some. The lathe chuck I did was really bad. So bad that it was almost completely stuck. All four jaws were like that. After about 3 days, I was able to get it disassembled easily, but it took several more days to get it completely clean. There were many fine pits on it, but that is because it was literally covered with rust. If the metal has been eaten away by rust, it will still be eaten away and there will be a pit, just no rust.

Also, the process is similar to chrome plating. It works better on "line of sight" to the anode, but it will work in hidden places. It just takes a lot longer. I read about a guy that had an old antique post drill that had been through a fire and looked completely hopeless. He hooked it up and left to go on a cruise (as on a ship) for several days. When he got back, he was able to get every bolt out with no issues. Almost seems like magic! It did work wonders on my old chuck, which also looked pretty hopeless.

FWIW - I found that using carbon for the anode works much better than iron. The iron anode will get a scummy covering of very nasty looking rust and the rust removal process slows down if it's not cleaned or replaced. Carbon doesn't do this, but will darken the water, leaving it black. Don't use stainless for the anode. This will release Hexavalent chromium into the solution. That's pretty nasty stuff.

Good luck.