Apparently it can be stripped with a mix of antimony trioxide and sulfuric acid 40% at 80 °C that will leave an antimony deposit, then to remove the antimony, a dip in nitric acid 30% at room temperature. Nitric acid is nasty and heavily regulated, so probably not a great solution. In the past I've just used sodium hydroxide/caustic soda in a heated solution, a teaspoon or two per gallon @ 130°F, I had a much larger tank and many years ago but those should be workable numbers. You have to pay attention as, depending on concentration and temperature, it acts quickly and will dissolve the aluminum as well. It will leave a black 'smut' that we removed with a nitric acid dip but after a rinse, it could be wiped of as well. Hot caustic soda baths will not kill you just for looking at them, or being in the general vicinity, but do require suitable safety precautions, after all, it's just lye that has been used as a drain cleaner for decades.
