Corrosion
Corrosion is the gradual destruction of metals caused by their reaction with substances in the environment such as oxygen, water, acids, or salts. The most common example is the rusting of iron, where iron reacts with oxygen and moisture to form hydrated iron oxides (rust). Corrosion weakens the metal, reduces its strength, and can cause damage to structures, machinery, and vehicles.
Corrosion as a Redox Process
Corrosion is essentially a redox (oxidation-reduction) reaction because:
- Oxidation of Metal (Anodic reaction):
- The metal atom (like iron) loses electrons and gets oxidized to metal ions.
- Example: Iron atoms lose electrons to form Fe²⁺ or Fe³⁺ ions.
- Reduction Reaction (Cathodic reaction):
- The electrons released during oxidation are consumed by another substance, usually oxygen in the presence of water.
- Oxygen is reduced to hydroxide ions (OH⁻) in a moist environment.
- Overall Redox Process:
- Oxidation (loss of electrons) happens at one site of the metal surface.
- Reduction (gain of electrons) happens at another site using the released electrons.
- Together, they form rust or other corrosion products.