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Practicals

Investigating Rusting
AKA: Iron Oxidisation

Summary

Iron nails are subjected to various conditions. Students investigate why rusting occurs in some but not all conditions.

Operation

Iron or steel nails are needed for this investigation, they need to be about 3-5 cm long. Make sure the nails are not galvanised (electroplated) as they will not rust, although galvanised types are usually required as well.

Ensure the nails are stored in a dry sealed packet between use. Painted nails are sometimes requested for this practical. To achieve this, push the nails into cork matting and paint at least two coats of enamel paint ensuring no bare nail is exposed. Make sure the paint is fully dry before using them.

Teachers may ask for some or all of the following equipment (per set):

  • Boiling tubes with bungs
  • Boiling tube rack
  • labels
  • Iron/steel nails
  • Boiled water
  • Painted nails
  • Galvanised nails
  • Vegetable oil
  • Magnesium ribbon
  • Copper foil strips
  • Salt water
The purpose of the practical is for students to subject the nails to differing conditions and after time, look at how much rust appears on each nail. They can then determine what conditions are required in order for iron to rust.

Each boiling tube holds a nail in water, salty water, water with oil on top, or just oil. Students may also use galvanised nails in all or some of the conditions and also may use the magnesium and copper strips to investigate sacrificial protection.

A strip of magnesium or copper is wrapped around each nail and placed in separate water filled tubes. The nail with the magnesium strip around it should have less rust than the one with the copper strip because the magnesium is more reactive and will corrode more readily than the nail whereas the copper is less reactive.

The painted and galvanised nails should not rust, showing that the paint and electroplating protects the surface of the nail from oxygen and moisture.

The tubes are usually labelled and left for a week or two. The tubes should not be disturbed and may sometimes be left in the preproom until required.

What is rust?

Many metals react with oxygen to form a compound that is a combination of that metal and oxygen. Iron reacts with oxygen to form iron oxide. The corrosion of iron and steel with water and air (oxygen) is called rusting.

Safety

 CautionThe contents of this page are for information only. Please refer to CLEAPSS or ASE safety advice and/or publications before undertaking any preparation, practical experiment or using any equipment featured on this site or any other.