The maglite is Aluminum, the D cells are steel. Use a bath of washing soda (Sodium carbonate), put the first battery back in and attach a wired to it, then plonk in the bath of soda and with a old steel whatever use that as an anode. Pass 12 V through it and let electrolysis remove all steel corrosion, the aluminum corrosion should chemically react and you get a mix of Aluminum Hydroxide and Carbonate. These should be easy to remove after.
The batteries should just drop out doing this. Unless you used Lithium batteries.....dont use the above with Lithium based batteries
The batteries should just drop out doing this. Unless you used Lithium batteries.....dont use the above with Lithium based batteries