Corrosion

Definition : 

It is defined as the destruction or deterioration and consequent loss of metals due to chemical or electrochemical attack on its surface by the environment. 

 OR

It is a process where a pure metal or alloy is transformed from its metallic state to the undesired combined state due to interaction with the environment through chemical or electrochemical attack.

Example:

1. Rusting of iron-a reddish brown scale formation on iron and steel objects. It is due to formation of hydrated ferric oxide.

2. Green scales formed on copper vessel.  It is due to formation of basic carbonate (CuCO₃+Cu(OH)₂).

Effect of corrosion:

1.    Loss of metal: The loss of metal due to corrosion as Rs.20000 crores per annum all over the world.

2.    Loss of useful properties of metal and result in loss of efficiency.

3.    Maintenance and production cost increases.

4.    Appearance: On rusting, reduced value of goods due to poor impression on the observer.

5.    Contamination of products stored in storage tanks due to chemical reactions.

6.    Loss of valuable products: The loss of uranium compounds is dangerous to environment.

7.    While handling hazardous materials such as conc.HCl, conc.HNO₃, explosive, the use of construction materials that minimize the corrosion failures.