Question

What is rusting? How is rusting prevented?

Answer 1

Definition

• Rusting is defined as the chemical process that involves the loss of $\mathrm{Iron}\left(\mathrm{Fe}\right)$ metal from the surface of the object in the presence of air and moisture.
• During rusting, $\mathrm{Iron}\left(\mathrm{Fe}\right)$ metal gets covered with reddish-brown oxide known as rust. Rust is also known as $\mathrm{Hydrated}\mathrm{Ferric}\mathrm{oxide}({\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O})$.
• Rusting takes place only in the presence of air and moisture.
• Rusting makes the object weak and unfit for use.
• Once it is started, it proceeds like a continuous process but it can be prevented if we take suitable precautions.

The chemical equation for rusting

$\underset{\mathrm{Iron}}{4\mathrm{Fe}\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}}{3{\mathrm{O}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{Water}}{\mathrm{x}.{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\to \underset{\mathrm{Hydrated}\mathrm{Ferric}\mathrm{oxide}}{2{\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}\left(\mathrm{s}\right)}$

Prevention

• Avoid contact: Rusting takes place in the presence of $\mathrm{Oxygen}\left({\mathrm{O}}_2\right)$ and water. So, avoid the contact of the object with air and moisture.
• Coat the surface of an object with oil or grease: Many machine parts and tools that are made from $\mathrm{Iron}\left(\mathrm{Fe}\right)$ metal should be coated with a thin layer of oil or grease when they are not in use. This prevents their contact with moisture and air and thereby prevents corrosion.
• Coating with paints: Bodies of cars, ships, trucks, and stairs should be coated with paints from time to time. This prevents the rusting by avoiding contact with objects with air and moisture.
• Coating with other metals: The process of coating a thin layer of $\mathrm{Zinc}\left(\mathrm{Zn}\right)$ on the surface of $\mathrm{Iron}\left(\mathrm{Fe}\right)$ the object is known as galvanisation. Because metal is unaffected by exposure to air and moisture. Thereby preventing corrosion.
• Conversion of Iron object into stainless steel: By cooling the molten $\mathrm{Iron}\left(\mathrm{Fe}\right)$ with a fixed amount of $\mathrm{Carbon}\left(\mathrm{C}\right),\mathrm{Chromium}\left(\mathrm{Cr}\right),\mathrm{and}\mathrm{Nickel}\left(\mathrm{Ni}\right)$ we get the stainless steel. It is inert to rusting.