Control Iron Rusting by Using More Electropositive Metal

The hull of the Titanic has rusted since it sank in 1912.

Ship hull is protected by rusting by bolting magnesium bar onto it.  How does magnesium bar protect the ship from rusting? Explain.                                                                 [2 marks]
  • Magnesium is more electropositive than iron. 
  • Magnesium loses electrons more easily than iron.
  • Mg --> Mg2+ + 2e-
  • Electrons move to iron. Therefore iron is protected by rusting

The same method is used controlling rusting of underground water pipes or steel utility pole. Blocks/stacks of magnesium is connected to the water pipes/steel utility pole by wires. Magnesium is  replaced from time to time when all magnesium corrodes.   This method is more known as sacrificial protection.

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