I had similar fun when an ultra thin diamond bead reamer broke off
and jammed in a semi-precious briolette. Nothing on my bench was
working to excavate delicately enough or shove strongly enough from
the back, and almost lost my second reamer trying.
Then after a couple days I thought of sewing needles and safety
pins. They’re amazingly hard stainless steel, sharp, and cheap–and
with safety pins you even get a built in “handle.” Worked like a
BTW, I was using water while I worked since I’d jammed a diamond bit
in stone, but for you with two metals, maybe mineral oil or WD-40?
My guess is corroding anything ferrous (and the portions you want to
corrode don’t have exposed surfaces) is probably a harder road than
digging it out and patching up the damage–even if it’s divots and