Tag: chemistry

The $Na^{\oplus}$ and $Cl^{\ominus}$ present in saline water increase the conductance of the solution in contact with the metal surface. This accelerates the formation of $Fe^{2+}$ ions and hence that of rust, $Fe _2O _3 \cdot xH _2O$

Rust is an iron oxide, usually red oxide formed by the redox reaction of iron and oxygen in the presence of water or air moisture. Given sufficient time, oxygen and water, any iron mass will eventually convert entirely to rust and disintegrate. No rusting takes place in absence of moisture. 

Oxide of iron is rust. Iron in presence of oxygen forms iron oxide. The chemical name of rust is ferrous oxide. It further oxidises to ferric oxide.

Cathodic protection: A technique to control corrosion of a metal surface by making it work as a cathode of an electrochemical cell by placing in contact with the metal to be protected another more easily corroded metal to act as the anode of the electrochemical cell. Most commonly used to protect steel, water pipelines, and storage tanks.

Anodic protection: A technique to control corrosion of a metal by making it work as anode developing a passive film on the metal. It used in extremely corrosive conditions and most extensively used to store and handle sulphuric acid container.

Hence, option A and C are correct

Correct statements are given below:

The presence of electrolyte increase the concentration of electron and thus increasing the mobility of electron due to which rate of corrosion increases.

Corrosion resistance of aluminium is due to formation of thin layer of aluminium oxide that forms when metal is exposed to air and prevents further oxidation. It is called as protective passivation.

Corrosion is basically oxidation of metal in presence of oxygen. So it can be prevented by cutting off ${ O } _{ 2 }$

Rusting of iron involves oxidation.