In the Rough Science programme 'The Reef', the Rough Scientists constructed a burglar alarm to protect the delicate coral reef off the island of Chumbe. They strung out a wire across the surface of the water to mark out a no-go region for boats. If a boat crossed the line the circuit was completed and the alarm sounded. Being an important nature reserve this had to be powered by an environmentally friendly source – wave power or sunlight. Rough Scientist Mikey B was given the challenge of stopping the wire rusting over time. He decided to use a lump of magnesium as a sacrificial electrode.
To find out more about how magnesium stops iron rusting and how it is used to protect oil drilling platforms and boats, read this extract from the second level OU course Our Chemical Environment (ST240).