C13 Preventing Corrosion

Question 1

Preventing rusting

Answer 1

• For rusting to happen air (oxygen) and water need to get to the iron.
• If we can stop either we stop rusting we can:
• Store the metal in pure nitrogen or argon gas (no oxygen)
• Desiccant powder (absorbs any water, even for the air)
• Painting (no air or water)
• Coating with plastic
• Coating in another metal (galvanising, usually we use zinc)
• Oiling or greasing.

Question 2

Sacrificial protection

Answer 2

• Instead of keeping air or water away we can ‘sacrifice’ another metal (let it corrode instead).
• Attach a chunk of magnesium or zinc to the iron. Mg and Zn oxidise much more easily as they are more reactive. Oxygen reacts with them instead of the iron or steel object.
• Over time the sacrificed metal will corrode away and you can attach a new bit.