I gave my wife an Olight I3E EOS Copper, w/Eneloop inside.
Eneloop died and she put a duracell in it w/o my knowledge.
NOW …. alki leaked inside - blackened & somewhat gaulded the threads.
O ring save the PCB!
Emitter still working but threads gritty, clunky and light flickering due to poor contact.
So I clean the threads with denatured alcohol on swab, polish the tube threads with Sunshine cloth, to removed acid blackening.
Clean again with denatured alcohol.
Pop in an Eneloop …. NADA
Damned shame, light had turned a beautiful patina … now its dead.
Soak the beastie in AcOH solution (white vinegar) to dissolve the yicky salts spewed by those vile hateful little alkaleaks. Might pit the outside Cu if left too long, so you might need to lightly sand/brush/otherwise abrade the outside to smooth it.
Use a Q-tip™ or generic cotton swab to get at the threads. Very very fine wire-brush if you got one, something to actually get into the threads.
It’s an uphill battle, one best to not have to do it in the first place. Trust me, I know all too well. Alcohols won’t do anything to get rid of the deposits.
Use Acetone because it will break up any deposits easy. Also, evaporates by air quickly so less chance of severe damage to already damaged areas caused by alkaleaks.