4.2.3 Corrosion in Other Metals

Last updated at April 25, 2026 by

What is Corrosion in Other Metals?

It is gradual deterioration of metal surfaces caused by air, water, or other substances .

Key Facts and Examples
  • Copper objects develop green coating when exposed to air .
Example: Copper vessels, copper wires, Statue of Liberty turns green
  • Silver objects develop black coating in moist air .
Example: Silver jewellery, silver coins turn black over time
  • Corrosion is similar to rusting but affects different metals .
Example: Iron rusts brown, copper corrodes green, silver tarnishes black
  • All metals except gold show some corrosion in atmosphere .
Example: Gold jewellery stays shiny, other metals need protection
Metal Corrosion Types Metal Type Corrosion Cause Iron - Brown rust Air + Water + Oxygen Copper - Green coating Air + Carbon dioxide Silver - Black tarnish Air + Hydrogen sulphide

🌟 Fascinating Fact: The wonder of ancient Indian metallurgy! The Iron Pillar of Delhi was made in the time of Chandragupta II more than 1600 years ago. It is about 8 metres high and weighs more than 6000 kilograms. Despite all these years of facing winds, rainfall, and intense weather, it has barely any rust.

Iron Pillar vs Modern Iron Property Ancient Iron Pillar Modern Iron Objects Age 1600+ years old Few years to decades Weather exposure Winds, rain, heat Similar conditions Rust formation Barely any rust Heavy rusting Special composition Pure iron + phosphorus Regular iron alloys Protection method Natural composition Artificial coatings needed

Section Summary: Effect of Air and Water on Metals: Iron

Effect of Air and Water on Metals: Iron Rusting of Iron Brown deposits from air + water Prevention Methods Painting, oiling, galvanisation protect iron Other Metal Corrosion Copper green, silver black coatings
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