Defining Corrosion
Corrosion is a natural electrochemical process that gradually destroys materials, usually metals, by chemical or electrochemical reaction with their environment. It transforms refined metals into more stable forms, such as oxides, hydroxides, or sulfides, which are less chemically active.
The Electrochemical Process
Most forms of corrosion involve an electrochemical reaction, where specific areas on the metal act as anodes (where oxidation occurs, and metal dissolves) and cathodes (where reduction occurs, often involving oxygen or hydrogen ions). An electrolyte, typically water containing dissolved ions, completes the circuit, allowing electron flow and material degradation.
Common Examples of Corrosion
The most familiar example is the rusting of iron, where iron reacts with oxygen and water to form hydrated iron(III) oxides. Other examples include the tarnishing of silver (forming silver sulfide) and the green patina that forms on copper statues or roofing (forming copper carbonates), which actually acts as a protective layer.
Impact and Prevention
Corrosion causes significant economic losses through infrastructure damage, equipment failure, and product spoilage. It can be prevented or mitigated through various methods such as protective coatings (paint, plating), cathodic protection, alloying with corrosion-resistant metals (e.g., stainless steel), and using inhibitors.