Corrosion — ক্ষয় (মরিচা)
Corrosion is the slow eating away of a metal by the oxygen, water or chemicals around it; rusting iron is the classic case.
Definition
Corrosion is the gradual destruction of a metal as it reacts with the oxygen, moisture, acids or salts in its surroundings. In humid air iron rusts into hydrated iron(III) oxide, ·x — the flaky brown coat on an old corrugated roof, a neglected railing or a bicycle left out in the rain. Silver blackens into silver sulfide, and copper slowly greens with patina. Corrosion wastes tonnes of metal every year, so we fight it with paint, grease, electroplating, a sacrificial coat of zinc (galvanizing) and alloys like stainless steel.
For example
One wet monsoon leaves the bolt of a rooftop gate red with rust; the same bolt, galvanized with zinc or painted, would have crossed the season untouched.