Corrosion and Its Prevention

📚 Key Concepts

🔹 Real-Life Example

Have you noticed how iron gates, car bodies, or old bicycles develop a reddish-brown coating over time? This is rust! The iron reacts with oxygen and moisture in the air to form iron oxide. That’s why ships are regularly painted, and cars are treated with anti-rust coatings. Corrosion costs billions of dollars annually in repairs and replacements.

Corrosion: Corrosion is defined as the slow and steady destruction of a metal by the environment. It results in the deterioration of the metal to form metal compounds by means of chemical reactions with the environment.

🧪 Important Formulas

🔸 Rusting Process

4Fe + 3O₂ + 2xH₂O → 2Fe₂O₃.xH₂O (Iron + Oxygen + Water → Hydrated Iron Oxide/Rust)

🔸 Conditions Required

• Presence of oxygen
• Presence of moisture/water
• Presence of acids (accelerates the process)

🔹 Prevention Methods

1. Painting: Creates barrier between metal and air

2. Galvanization: Coating with zinc

3. Oiling/Greasing: Prevents moisture contact

4. Alloying: Making stainless steel

 5. Electroplating: Coating with non-reactive metals

🔍 Advanced: Galvanization Process

Zinc is more reactive than iron, so it gets oxidized first, protecting the iron underneath. Even if the zinc coating gets scratched, the exposed iron remains protected because zinc continues to sacrifice itself.