Removing broken studs, bolts, taps, etc from brass and aluminum

SouthArk370Z

UPDATE: I used a ceramic coffee mug to hold the alum solution (it will eat up ferrous containers), during the procedure. Can't tell if there is some residue left on the bottom of the cup or if the alum ate into the glaze but I've tried soaking in hot water, soaking in warm vinegar, and scrubbing with Comet - it's there to stay. Shouldn't affect it's use for another run, but I wouldn't want to drink out of it now. Should be safe (alum is not harmful in small quantities - it's used as a "food crisper") but, damn, it looks ugly.

Might be because I added way too much alum at the start (about twice what was needed for a saturated solution).

Next time I have a strong acid (muriatic, sulfuric, etc) out, I'll see if that will remove it.

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