Rusting

1. Presence of iron
2. Presence of moisture (water)
3. Presence of oxygen (air)

Demonstrating conditions necessary for rusting of iron nails

To understand what is needed for rusting to occur, we can use iron nails and test them under different conditions.

Materials Needed

1. Iron nails
2. Four dry test tubes (labeled A, B, C, and D)
3. Cotton wool
4. Tap water
5. Boiled tap water
6. Oil
7. Crystals of anhydrous calcium chloride

What to Do (Procedure):

1. Put two clean iron nails into each test tube (A, B, C, and D).
2. In test tube A, place some wet cotton wool (add tap water to make it wet).
3. In test tube B, pour some boiled tap water, then add oil on top to prevent air from entering.
4. In test tube C, place dry cotton wool and add some crystals of anhydrous calcium chloride (which absorbs moisture).
5. In test tube D, do not add anything—just leave the nails exposed to air only.
6. Leave all test tubes open to air and observe after three days.

Observation

• Rusting will only occur in test tube A, where both water and air (oxygen) are present.
• No rust will form in B, C, and D because at least one of the rusting conditions is missing.

Conclusion

For rusting to take place, both water and air (oxygen) must be present.

1. Oiling and Greasing Applying oil or grease forms a protective layer that keeps out air and water. Used for:

   • Door locks
   • Bicycles
   • Motorcycles
   • Machine parts

2. Painting Painting iron surfaces forms a protective barrier that prevents oxygen and water from reaching the metal. Used for:

   • Gates
   • Roofs
   • Window grills

3. Galvanizing This is covering iron or steel with a thin layer of zinc, usually by dipping the iron in molten zinc. Zinc reacts with air to form zinc oxide, which protects the iron from rust.

4. Electroplating Iron is coated with another metal such as tin, silver, chromium, or nickel using electric current. Common electroplated items:

   • Spoons
   • Forks
   • Knives
   • Graters

5. Enameling Iron is coated with enamel, a smooth, stony material that adds both protection and decoration. Used for:

   • Steel plates
   • Steel cups
   • Steel jugs

6. Alloying This involves mixing iron with other metals to form an alloy that is more resistant to rust. Example:

   • Stainless steel (a mixture of iron, chromium, and nickel) does not rust easily. Used for:
   • Kitchen utensils
   • Medical tools
   • Construction materials

7. Plastic Coating Iron can be coated with a layer of plastic to keep out moisture and air. Used for:

   • Outdoor furniture
   • Fences
   • Tools with plastic handles