why is zinc used to coat iron in galvanising even if it is more reactive than iron
The 'rusting' corrosion can be prevented by connecting iron to a more reactive metal such as zinc.
- This is referred to as sacrificial protection or sacrificial corrosion as the more reactive protecting metal is preferentially oxidised away, leaving the protected metal intact.
- Theoretically, any iron ions formed by oxidation would be reduced by electrons from the oxidation of the more reactive 'sacrificed' metal.
- All the methods used ensure the iron or steel corrodes less readily than pure iron.
- Blocks of a more reactive metal like zinc can be bolted to the steel hulls of ships or underground iron pipes and the more reactive zinc atoms preferentially lose electrons rather than the iron, i.e. the zinc stops the iron rusting.
- So the zinc corrodes away leaving the iron intact.
- Sacrificial corrosion does not mean displacement reaction.
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