Why does Aluminum Oxide not degrade Aluminum metal formed over it whereas Iron Oxide degrades Iron Metal (Rust)?

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Solution

Dear student!
Aluminium oxide is quite hard, and is used on abrasive sheets. It tends to corrode heavily if it's in contact with Oxygen. But at the result, Aluminium oxide builds a very thin and robust layer (passivation layer) which is impermeable to water and oxygen and that protects the metal from further corrosion or degradation.
While the iron oxide, forms a permeable oxide which allows the passage of both the oxygen and water so that they reach to the metal surface and further corrode it, and the corrosion occurs by iron oxide.

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Fill in the following balnks with suitable words:

(a) Metals are ........................... conductors of heat and ............................

(b) Most non-metals are ........................... conductors of heat and ...........................

(d) Metals react with acids to produce ........................... gas.

(e) Iron is more ........................... than copper.

(f) Metals form ........................... oxides whereas non-metals form ........................... oxides.

(g) Sulphur forms ........................... oxide whereas magnesium forms ........................... oxide.

(h) A non-metal is used to make an antiseptic solution called tincture ...........................

Why copper and aluminum are used over tungsten, iron, nickel to make fuses?

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