You use an acid flux to remove the oxidation on aluminum. Guess what your sweat will do if it is acidic enough? Hobo soldering tip 101 - no flux, use your sweat

You use an acid flux to remove the oxidation on aluminum. Guess what your sweat will do if it is acidic enough? Hobo soldering tip 101 - no flux, use your sweat if you can get away with sodium in your solder and your solder has no flux.