Dear student,

The surface of some metals acquires a dull appearance when exposed to air for a long time because metals form a thin layer of oxides of carbonates or sulphides on their surfaces by the slow action of various gases present in the air that make the dull appearance.

That's why it is necessary to coat them with a layer of some non reactive alloy or galvanize it.

The surface of some metals acquires a dull appearance when exposed to air for a long time because metals from a thin layer of oxides, carbonates or sulphide on their surface by the slow action of various gases present in the air that make the dull appearance.

I hope my answer helps. All the very best for your future endeavors!

hello aspirant,

The surface of some metals acquires a dull appearance when exposed to air for a long time because metals from a thin layer of oxides, carbonates or sulphide on their surface by the slow action of various gases present in the air that make the appearance dull.an example could be aluminium which reacts to form a layer of aluminium oxide on its surface, the reason why aluminium foil is unreactive unless the oxide layer is removed.

hope this helps.