Some metals lose their lustre when exposed in the air. Why?
The metals lose their shine or lustre on keeping in the air for a long time due to formation of a thin layer of oxide, carbonate or sulphide on their surface by the slow action of various gases present in the air. This is known as Rusting.
In order to protect the metals from Rusting, the iron part is coated with zinc by the process of Galvanisation.
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