Aluminium is said to be more reactive than iron, towards oxygen (or air).Yet iron undergoes corrosion to a greater extent than aluminium.Explain.
Aluminium forms a white colour oxide on exposure to the atmosphere. This white colour oxide prevents it from further corrosion whereas iron reacts with air to form hydrated oxide called rust. So, iron undergoes corrosion to a greater extent.
Aluminum develops a protective layer of aluminum oxide by slowly reacting with oxygen present in air.
After this layer formation , air can't react with aluminum present,hence there is only less corrosion.
In compare , iron can't form protective layer hence it easily gets corroded.