Question

The main factors which affect corrosion are:
A. Position of metal in electrochemical series
B. Presence of CO$_2$ in water.
C. Presence of impurities coating
D. All are correct.

Answer 1

Hint: Corrosion is the process of converting a refined metal into a stable form such as oxide, hydroxide, or sulphide. It happens due to the atmospheric gases on the surface of the metal. This definition can help us to the main factors affecting the corrosion.

Complete step by step answer:
a) First, we know about the process of corrosion. It includes rusting of iron, tarnishing of silver, development of green coating on copper, and bronze.
b) Now, talking about the first option i.e. it is about the position of metal. The more will be the reactivity of metal in the electrochemical series, the more will be the possibility of the metal being corroded.
c) If we look at the second option; it is about the presence of carbon-dioxide (CO$_2$) in water. The rusting of iron happens only due to this factor.
d) The third option is the presence of impurities. We can take the example; when the iron surface is coated with the layers of metals more active, or reactive than iron, then the rate of corrosion is retarded.
e) We can conclude that all the given options are correct.

So, the correct option is D.

Additional Information:
1. By coating a thin layer of any other metal which does not corrode.
2. By painting the surface of metal.

Note: Don’t get confused about how the presence of carbon-dioxide in water facilitates the rusting of iron. CO$_2$ from the atmosphere, reacts with water to form carbonic acid, and carbonic acid provides protons which are necessary for the oxidation of iron.