Question

What is the main cause of corrosion?

Answer 1

Hint: Corrosion is the general eaten up of metal when it comes in contact with the surrounding. Whenever the metal comes in contact with oxygen, water, hydrogen, electric current or even bacteria, the metal surface forms a layer of oxide and thus corrodes.

Complete answer:
Corrosion is generally eaten up by metal gradually when it comes in contact with the atmosphere. There are numerous reasons for this corrosion. Some of them are as follows:
$1.$ The content of humidity in air affects the metal. If the amount of humidity is much larger in the air then there will be corrosion of the metal. Also, the water vapour condenses on the metal surface and then it reacts with metal which is the main cause of corrosion.
$2.$When the metal is exposed to electric current for a longer period of time, then the metal surface forms a layered oxide due to the flow of electric current. Hence the oxide layer gradually increases and weakens the metal.
$3.$ There are numerous gases present in the environment which may also cause corrosion of metal. The gases like chlorine, hydrogen oxides, ammonia also cause corrosion of the metal. Such gases are reactive in nature and react with metal.
$4.$ Rusting is the common form of corrosion that actually takes place on iron metal. When the piece of iron metal is left exposed to the water vapour region it gets corroded easily. Rusting can be prevented by oiling the metal surface.
$5.$ The presence of salts in water also causes corrosion. Salty water favours corrosion.

Note:
Corrosion can be in any form of oxides or sulphides. It may be in the form of rust or it may be in the form of a change of colour or it may be in the form of holes generated in metals. Therefore corrosion weakens up the metal by eating up the metal gradually.