Question

Explain the term corrosion with an example. Write a chemical equation to show the process of corrosion of iron.

Answer 1

Corrosion is a process where a metal slowly and gradually degenerates due to the chemical reaction of different gases and moisture present in the atmosphere on that particular metal. Corrosion of iron takes place when it is exposed to atmosphere and water for long hours.

Complete step-by-step answer: Let us first understand the concept of corrosion. Corrosion occurs when a metal is exposed to atmospheric gases and moisture. This metal reacts chemically with these gases and moisture and gradually degenerates or degrades and this process of breaking down of a metal is known as corrosion.Metals that undergo corrosion usually form oxides, hydroxides and sulfides of that metal. There are different types of corrosions. Some of them can be listed as intergranular corrosion, galvanic corrosion, stress corrosion, crevice corrosion etc.Let us understand this concept of corrosion with an example. When materials made of the metal copper are exposed to the atmosphere, copper oxidizes to form copper oxide.We can write this reaction as $2Cu + {O_2} \to 2CuO$
This process of corrosion of copper is known as patina.When iron is exposed to the atmosphere, initially it reacts with oxygen to form ferrous oxide and then reacts with the water molecules forming rust.We can write an equation for this reaction as follows.
$Fe + \dfrac{1}{2}{O_2} + 2{H_2}O \to F{e_2}{O_3}.x{H_2}O + 4{H^ + }$

Note: It is to be noted the rate of corrosion of a metal depends on its reactivity which means that the more active a metal is the easier it is to undergo the process of corrosion. Several types of coats and paints are being used to prevent the metal from reacting with the atmosphere to eliminate its corrosion.