"Wild_Bill" fired this volley in
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aluminum oxide is what many abrasive products are
made of, and not particularly easy or cost effective to attempt remval
with mechanical methods.



Unless you "flux" the surface _while_ you are cleaning, the oxide layer
will re-form as rapidly as you clean. Aluminum is extraordinarily
reactive with water and oxygen, and reacts almost instantaneously when a
fresh layer is uncovered.

Bases are actually more effective at removing aluminum oxide than are
acids.

It's the base/Al2O3 reaction in aluminum-bearing pyrotechnic compositions
that can cause thermal run-away in the presence of moisture. The Al2O3
protects the surface from reacting with water, but basic solutions
quickly dissolve it (but not the base metal, as would an acid), exposing
the pure metal to water attack.

LLoyd