Question

aluminum is placed above iron in the activity series and thus said to be more reactive towards oxygen than iron.yet iron undergoes corrosion to a greater extent than aluminum-explain

Answer 1

Because even though aluminum is more reactive than iron it does not corrode as much as iron. Aluminum reacts with oxygen in the air to form a layer of oxide which protects the aluminum from further oxidation. On the other hand the oxides of iron (rust) tend to fall away, exposing the unreacted iron to further oxidation.

Answer 2

Iron and steel rust when they come into contact with water and oxygen. They rust faster in salty water or acid rain.