Short Answer:

Galvanization is the process of coating iron or steel with a layer of zinc to protect it from corrosion and rusting. The zinc layer acts as a barrier and also provides sacrificial protection, preventing the iron underneath from corroding.

For example, iron pipes, sheets, and rods are often galvanized to increase their durability and lifespan, especially in humid or outdoor environments. Galvanized iron is widely used in construction, infrastructure, and household applications because it is rust-resistant and long-lasting.

Detailed Explanation:

Galvanization

Galvanization is a method used to protect iron and steel from rusting by applying a coating of zinc. Iron and steel are prone to corrosion, especially when exposed to moisture and air. Zinc protects the metal in two ways: it forms a physical barrier and acts as a sacrificial anode, meaning it corrodes in place of iron when exposed to air and moisture.

Methods of Galvanization

1. Hot-Dip Galvanization:
   • Iron or steel is dipped into molten zinc at high temperatures.
   • A uniform layer of zinc adheres to the surface, providing excellent protection.
   • Common for structural steel, pipes, and sheets.
2. Electrogalvanization:
   • Zinc is deposited on iron or steel using electrolysis.
   • Produces a thinner, more controlled zinc coating.
   • Suitable for small components, nuts, bolts, and automotive parts.
3. Sherardizing:
   • Iron or steel is heated with zinc powder in a rotating drum, causing zinc to diffuse into the surface.
   • Used for small parts requiring uniform protection.

How Galvanization Protects Iron

1. Barrier Protection:
   • The zinc layer prevents air and moisture from reaching the iron surface.
   • Rusting is slowed or completely prevented as long as the coating remains intact.
2. Sacrificial Protection:
   • Even if the zinc layer is scratched, zinc corrodes preferentially.
   • Zinc loses electrons more easily than iron, so it protects the iron underneath through cathodic protection.
3. Durability:
   • Galvanized iron lasts 5–50 years depending on thickness, environment, and maintenance.

Applications of Galvanized Iron

1. Construction:
   • Roof sheets, beams, doors, and structural frameworks.
2. Infrastructure:
   • Fencing, pipelines, bridges, and railway tracks.
3. Household Items:
   • Water tanks, utensils, nails, screws, and corrugated sheets.
4. Automobiles and Machinery:
   • Car bodies, chassis, and industrial equipment exposed to moisture.

Advantages of Galvanization

• Corrosion Resistance: Protects iron in humid or outdoor environments.
• Long Lifespan: Reduces maintenance and replacement costs.
• Economic: Zinc is relatively inexpensive and effective for protection.
• Mechanical Strength: Zinc coating does not reduce the strength of iron or steel.
• Ease of Application: Can be applied to large and small components using different methods.

Limitations

• Thick coatings may crack under severe stress.
• Galvanized coatings may corrode in highly acidic or alkaline environments.
• Requires maintenance in extremely aggressive environments (e.g., marine).

Summary

Galvanization is the process of coating iron or steel with zinc to prevent rusting. It provides a barrier and sacrificial protection, extending the life of metals in construction, infrastructure, and household applications.

Conclusion:

Galvanization is a highly effective method to protect iron and steel from corrosion. By applying zinc coatings through hot-dip, electrolysis, or other methods, metals gain long-lasting durability, resistance to rust, and improved lifespan. It is widely used in construction, infrastructure, automotive, and household items, providing both economic and functional benefits.