Question

What is corrosion? Why is corrosion only a problem in some metals (such as iron)?

Answer 1

Solution:

Any process of deterioration (or destruction) and consequent loss of a solid metallic material, through an unwanted (or unintentional) chemical or electrochemical attack by its environment, starting at its surface, is called corrosion. Thus, corrosion is a process "reverse of etraction of metals"

The process of corrosion are carried out by oxidation process (oxygen) and rest other gases also involves but oxygen is a main culprit in corrosion process.

The most familiar example of corrosion is rusting of iron, when exposed to the atmospheric conditions. During this, a layer of reddish scale and powder of oxide (Fe₃O₄)is formed, and the iron becomes weak.

The general reaction of oxidation corrosion are:

2M   ------>     2Mn⁺ + 2ne^-       (Loss of electrons)

(n/2)O₂ + 2ne^-    --------->      nO₂^-       (Gain of electrons)

(or)

2M + (n/2)O₂    ---------->      2Mn⁺ + nO₂^-