Why does Aluminium metal items which shines like silver when new, turns dull gray after sometime?

Dirt sticks quickly to Al metal surface

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Chemicals of dish washing brings about a change

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Protective layer of $A l_{2} O_{3}$ forms on metal surface

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Solution

The correct option is C
Protective layer of $A l_{2} O_{3}$ forms on metal surface

The Aluminium metal items undergo oxidation when exposed to atmospheric Oxygen and water, slowly forms a protective layer of $A l_{2} O_{3}$ over the metal surface which makes the metal look dull.

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Similar questions

	Appearance	Reaction with dilute $H C l$	Reaction with dilute $H N O_{3}$
Unknown metal #1	Dull gray solid with white oxide coating	Dissolved with bubbles of clear gas	Dissolved with bubbles of clear gas
Unknown metal #2	Solid; lustrous, smooth silver-gray surface	No reaction	Dissolved with bubbles of orange gas

	Appearance	Reaction with dilute $H C l$	Reaction with dilute $H N O_{3}$
Unknown metal #1	Dull gray solid with white oxide coating	Dissolved with bubbles of clear gas	Dissolved with bubbles of clear gas
Unknown metal #2	Solid; lustrous, smooth silver-gray surface	No reaction	Dissolved with bubbles of orange gas

H N O_{3}

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