Corrosion:

• Corrosion is the gradual deterioration of metals due to their reaction with environmental factors such as oxygen, moisture, and pollutants.
• Example: Rusting of iron.

Causes of Corrosion:

• Presence of Moisture: Water in the environment facilitates the oxidation of metals.

• Oxygen: Combines with metals to form oxides.

• Pollutants: Gases like sulfur dioxide and carbon dioxide accelerate corrosion.

Examples of Corrosion:

• Iron: Rusts to form hydrated ferric oxide (Fe₂O₃·xH₂O).

• Copper: Forms a green layer of basic copper carbonate (patina).

• Silver: Tarnishes to form silver sulfide (Ag₂S).

• Aluminium: Forms a protective layer of aluminium oxide (Al₂O₃).

Rusting of Iron:

• Reaction: 4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃, which dehydrates to Fe₂O₃·xH₂O (rust).
• Rusting is a specific type of corrosion that weakens iron structures.

Factors Affecting Corrosion:

• Humidity: High moisture levels increase corrosion.

• Temperature: Higher temperatures accelerate chemical reactions.

• Impurities: Saltwater and acidic pollutants enhance corrosion rates.

Prevention of Corrosion:

• Coating and Painting: Creates a protective barrier against moisture and air.

• Galvanization: Coating iron with a layer of zinc.

• Alloying: Mixing metals to improve corrosion resistance (e.g., stainless steel).

• Electroplating: Depositing a layer of a less reactive metal on the surface.

• Cathodic Protection: Using a more reactive metal as a sacrificial anode to protect the main metal.

• Greasing or Oiling: Prevents moisture contact with the metal surface.

Impact of Corrosion:

• Weakens metal structures, reducing their strength and durability.
• Causes economic loss due to the replacement and maintenance of corroded materials.
• Leads to safety hazards, especially in bridges, buildings, and pipelines.