1. Corrosion of metals

2. What is corrosion?
Corrosion is the gradual destruction of a metal due to reactions with other chemicals in its environment.
Over time, corrosion changes the appearance of the metal as it breaks down and it becomes weaker.
Corrosion can seriously damage metallic objects and structures.
Coating the surface of a metal with paint and certain chemicals can protect it from corrosion.
What happens if the protective coating becomes damaged?

3. Do all metals corrode?
Metals behave differently when exposed to the environment.
Gold is an unreactive metal and does not corrode easily.
In many cultures, gold is considered a precious metal and is used to make sacred and decorative objects.
Items made from gold can survive for thousands of years and have even been found in good condition underwater.
In general, objects made from metals that corrode easily do not survive for as long.

4. Why doesn’t aluminium corrode?
Aluminium is a very reactive metal. However, it does not corrode in the presence of oxygen. Why is this?
oxygen in the atmosphere
coating of oxygen atoms
aluminium atoms
The outer aluminium atoms react with oxygen in the atmosphere. This forms a thin layer of aluminium oxide on the metal’s surface which protects the metal from corrosion.

5. What is rusting?
Rusting is the specific name given to the corrosion of iron.
It is a chemical reaction between iron, oxygen and water.
The chemical name for rust is hydrated iron oxide. Rust can form on cars and buildings, making them unsafe. It is an expensive problem.
Salt can increase the rate of rusting. This iron bolt is on a seaside structure and is nearly completely corroded.
What is the word equation for the formation of rust?
hydrated iron oxide
water + 
iron
oxygen