Caustic soda 90% pure, 1-3 in water (add soda to water, not the other way around).
Fumes are hydrogen, don't smoke.
10 minutes should be enough.
Rinse in acetic acid (vinegar) to neutrilise the caustic soda. this will also help with sludgy bits in hard to get to cavities. Then flush with water, lots and lots of water.
Add acetic acid to your mix and let settle, then tip it through a fine gauze to take out the aluminium salts you've made. then dispose of liquid safely.
wear gloves, goggles and long sleeves, caustic burns are not fun.