Question

Corrosion of metals involves:
(A) Physical reaction
(B) Chemical reaction
(C) Both A and B
(D) None of the above

Answer 1

Hint: We already know that there are two types of reactions such as physical reactions and chemical reactions. We will first see the definition of corrosion and the difference between these two types of reactions. This will help us to determine the type of reaction that is taking place in the corrosion process.

Complete answer:
Physical reactions are those reactions which are reversible in nature and in this reaction no new compound is formed. While chemical reactions are those reactions which are not reversible in nature and in this reaction new compounds are formed.
We know that corrosion is a process in which the metal is eaten up by the acid, moisture, and oxygen that is present in the air. In this process a coloured layer gets deposited on the metal surface.
So, this layer is deposited on the metal surface when the metal reacts with oxygen or any other chemical present in the surrounding.
Hence, the metal cannot be recovered back after corrosion and we can say that corrosion is a chemical reaction.
Therefore, the correct option is (B) Chemical reaction.

Note:
We should not get confused between the terms corrosion and rusting. Corrosion as we have defined it is a reaction in which the metal is eaten up by the acid, moisture, oxygen that is present in the air. While rusting is the name given to the corrosion of iron objects only. Hence, rusting is a type of corrosion.