Study Guides/Chemistry/Galvanization and Galvanized Iron
Study Guide · Chemistry

What is Galvanization? (Galvanized Iron Explained)

Galvanization (or Galvanisation) is the process of coating iron or steel with a thin layer of zinc to protect it from rusting (corrosion). The end product is called Galvanized Iron (GI). This is one of the most effective and cost-efficient methods of preventing corrosion at a large scale.

Question (Click to Flip)

Is galvanization permanent?

Answer

No, it is not permanent. The zinc coating gradually corrodes (forming a protective layer of zinc oxide/carbonate called 'white rust'), but this process is much slower than iron rusting. A typical galvanized coating lasts 20-50 years depending on the environment.

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Key Facts

Galvanized iron pipes were historically used for household water supply, but are now largely replaced by PVC and CPVC pipes. Galvanized steel is still widely used for roofing sheets, buckets, and wire fencing.

In Hindi, galvanization (गैल्वनीकरण) is sometimes called 'जस्ता चढ़ाना' (jastha chadhana), meaning 'coating with zinc'.

Why Does Zinc Prevent Rusting?

Zinc acts as a sacrificial anode. Even if the zinc coating gets scratched and the iron underneath is exposed:

  1. Zinc is more reactive than iron.
  2. Zinc reacts with oxygen and moisture preferentially instead of allowing iron to rust.
  3. The zinc 'sacrifices' itself to protect the iron underneath.

This principle is called Cathodic Protection or Sacrificial Corrosion.

The Galvanization Process

The standard industrial method is called Hot-Dip Galvanizing:

  1. The iron/steel object is thoroughly cleaned (degreased and pickled in dilute acid) to remove all rust and oxide layers.
  2. The clean iron is then dipped into a bath of molten zinc at approximately 450°C.
  3. The iron is withdrawn, and the zinc solidifies as a thin, strongly-bonded coating.

Other methods: Electroplating (electrogalvanizing) is used when a very thin, uniform zinc layer is needed (e.g., for car body panels).

Questions and Answers

Is galvanization permanent?+

No, it is not permanent. The zinc coating gradually corrodes (forming a protective layer of zinc oxide/carbonate called 'white rust'), but this process is much slower than iron rusting. A typical galvanized coating lasts 20-50 years depending on the environment.

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