Rusting of iron is the most common example of corrosion. It is an oxidation process that occurs when iron is exposed to moisture and oxygen. It is a fundamental concept in Class 10 Chemistry.
Rust is soft, porous, and flaky. Unlike the tarnish on aluminium (which protects the metal underneath), rust constantly flakes off, exposing fresh iron to the air, eventually destroying the entire object.
The overall chemical equation for the rusting of iron is:
4Fe(s) + 3O₂(g) + 2xH₂O(l) → 2Fe₂O₃·xH₂O(s)
Where:
The 'x' in the formula of rust (Fe₂O₃·xH₂O) represents a variable number of water molecules of crystallization. The exact number of water molecules depends on the humidity and moisture present in the environment when the rust forms.
For rusting to take place, two conditions are absolutely essential:
Galvanisation is a widely used method to prevent rusting. It involves coating iron or steel objects with a thin layer of **Zinc (Zn)**. Zinc acts as a sacrificial barrier, corroding before the iron does.
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