What is corrosion? `CO_2` is always present in natural water. Explain its effect (increases, stops or no effect) on rusting of Fe.

Explanation

Corrosion is a process of slowly eating away of the metal due to the attack of atmospheric gases on the surface of metal resulting into the formation of compounds such as oxides, sulphides, carbonates, sulphates, etc.
Factors affecting corrosion are:
(i) Reactivity of metal.
(ii) Presence of impurities
(iii) Presence of air and moisture
(iv) Strains in metals
(v) Presence of electrolytes.
`CO_2` increases the rusting of iron greater the number of `H^+` ions, faster the rusting will take place.