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

SouthArk370Z

Found a neat trick. If you break off a steel stud, bolt, tap, etc. in a piece of brass or aluminum, here's a great way to get it out. It's slow, but it works.

Get some potassium aluminum sulfate (AKA alum) at the grocery store - it will probably be in the canning section.

Set up a double boiler and add about 1 oz of alum per cup of water. Heat up the boiler and add more alum until the solution is saturated (no more alum will dissolve).

Dunk the part in the hot alum and let soak for several hours to several days (depending on the size of the broken part, what kind of steel it is, concentration of solution, and temperature). The hot alum will corrode the steel part but not the brass or aluminum.

I have tried this with a brass manifold from a Coleman lantern that had a stud broken off in it - worked great. Haven't tried it with any aluminum parts, yet.

Use appropriate safety equipment as you will be messing around with a hot, strong, alkaline liquid - goggles, gloves, ventilation, etc - it's not poisonous, but it will be very basic. If you get some of the alum solution on your skin, rinse well with cool water. I did it on my kitchen stove with the exhaust fan going.

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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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