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Removing frozen bolt from aluminium and alloys with Alum

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tore:
I had many bolts and studs that snapped right off when I tried to remove them. Most in the size of M5 and M6. Common for all of those is that the holes are made of aluminium or alloys of aluminium. All bolts are made of steel.

Steel are harder and the size of the bold make it a bit difficult to drill out without ruin the threads.

I came across Alum (potassium aluminum sulfate), available in a grocery store. Alum does not affect the aluminium or its alloys. The Alum should be mixed in water and heated before it has any effect. As more alum in the solution as more effective. And of course the opposite, cool down the mixture and the alum will crystalize and sink to the bottom. Many youtube videos show this process where a small part is fully covered in a alum water mixture. Heat applied and it start to bubble at the steel part.
I figured that this process will not work for any larger part (such as a barrel or a crank case) since the part is either too big to get fully submerged or cool down the mixture too much once put in the mixture.
If the part is partially in the mixture it will cool down the mixture. The Alum will crystalize and build a coat on the part. That will inhibit the process.
So the part has either to be fully covered with the mixture from cold or the whole piece with mixture is placed in an oven.
Alum is very efficient if you do it right.

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