I've been following this thread with interest; it's been ages since I broke a tap in aluminium, so it's bound to be my turn again soon. I have been trying to find out what alum actually is. "True alum" seems to be the double sulphate of aluminium and either potassium or ammonia *, whereas "papermaker's alum" seems to be just hydrated aluminum sulphate. Which of these "alums" will attack taps broken off in aluminium, or will any of them work?
And will the process work for brass, too?
* apparently, there was once a thriving trade in human urine here in the UK, to supply the Yorkshire alum makers with ammonia, when they weren't burning seaweed to get potassium!
Andy
Ian Foster <fosterscons@...> wrote:
Oh no John, No John, No John, No!
G'day all, (had to include that!)
Alkalinity increaser will raise the pH whereas Alum lowers the pH. You
want a very ionic solution with a low pH which will attack the iron
without attacking the aluminiun oxide. Whilst aluminium is more
electropositive than iron its oxide protects it from attack by the acid
radicals. To help, aluminium sulphate is insoluble and forms a
protective coating also. (This does not apply to aluminum sulfate
unless you stir vigourously.) Interestingly the Electrolytic Zinc works
in Hobart Tas. would not allow gavanized steel cable ladder but would
allow aluminium due to the suphurous atmosphere.
I have wondered whether Ammonium Sulphate would also work, it is quite
corrosive to iron and is available as a fertiliser (as are most of my
comments). If you could get it withour raising suspicsion, ammonium
nitrate might also work.
BTW, Alum is a styptic which causes blood to clot, if your barber cuts
you he will have a bottle of alum solution to apply to the cut.
One good turn deserves another.
Regards,
Ian
--- In 7x12minilathe@..., "born4something" <ajs@...> wrote:
--- In 7x12minilathe@..., "Jeff Demand" <jdemand@>
wrote:
And don't drink it, tastes awful and will rot your teeth ;-).
Hi Jeff,
How about dentures? <G>
More seriously, would I be correct in assuming this bag of Alkalinity
Increaser I have in the corner would be the same stuff?
John
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