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Aluminum metal covers itself immediately of an oxide layer in air. This layer is quite thick, more than 0,01mm they say and it's non-conductive. This layer infact is, e.g., thick enough to prevent soldering, further chemical attack by air oxygen or water (with which nude Al would immediately react) or discharge of many kinds of ions in solution (for example it doesn't react with Cu++, unless Cl- ions or other catalyzing agent added).
Why then a piece or a thread of Al metal is conductive? That is, how can it conduct an electric current when is touched with electric cables (connected to a battery)?
Why the mechanism, whatever it is, which allows the passage of electric current through the Al2O3 layer, doesn't allow ions discharge at its surface?
(Clearly there are other materials that shows this behavior, Al is just an example).
Thanks.
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lightarrow
Why then a piece or a thread of Al metal is conductive? That is, how can it conduct an electric current when is touched with electric cables (connected to a battery)?
Why the mechanism, whatever it is, which allows the passage of electric current through the Al2O3 layer, doesn't allow ions discharge at its surface?
(Clearly there are other materials that shows this behavior, Al is just an example).
Thanks.
--
lightarrow