Because zinc act as resistor of atmosphere.it can not come with direct contact with atmosphere.

Zinc Coating and Galvanisation
Galvanisation is a process used to protect steel and iron from corrosion through the application of a zinc coating. This method is essential in various industries due to its effectiveness in prolonging the lifespan of metal structures.

What is Galvanisation?
Galvanisation involves immersing the metal in molten zinc or applying a zinc coating via electroplating. The resulting layer acts as a barrier against moisture and environmental factors that can lead to rust and degradation.

Why Zinc?
- Corrosion Resistance: Zinc has excellent anti-corrosive properties, making it suitable for protecting ferrous metals.
- Electrochemical Protection: Zinc acts as a sacrificial anode; if the coating is scratched, the exposed steel will corrode at a much slower rate, as the zinc corrodes first.
- Durability: Zinc coatings can last for decades, even in harsh environments, significantly reducing maintenance costs.

Applications of Galvanisation
- Construction: Used in beams, roofing sheets, and nails to enhance durability.
- Automotive Industry: Protects car bodies and parts from rusting due to exposure to moisture and road salts.
- Infrastructure: Ideal for bridges, railings, and utility poles, providing long-lasting protection.

Conclusion
Galvanisation is a vital process that employs zinc to safeguard metals from corrosion. Its widespread application across various sectors highlights its importance in maintaining the integrity and longevity of metal structures.