Corrosion is the deterioration of a material, or of its properties, as a consequence of reaction with the environment.

In addition to corrosion of metals—the effects of soil, atmosphere, chemicals, and temperature serve as agents of corrosion for a number of materials. The need to understand and control corrosion has given rise to the new sciences of corrosion technology and corrosion control, both of which are solidly based upon chemistry and geochemistry.

Perhaps the earliest recognition of corrosion was the effect of seawater and sea atmospheres on ships. Salt water, continual dampness, and the growth of marine life such as marine borers, led to the decay of wooden hulls. Because of its toxicity, copper cladding of the hulls was widely used to discourage marine growth. In 1824, to protect the copper from deterioration, the team of English scientists Humphrey Davy (1778-1829) and Michael Faraday (1791-1867) applied zinc protector plates to the copper sheathing. This was the first successful application of cathodic protection, in which a more readily oxidized metal is attached to the metal to be protected. This procedure was widely used until hulls were replaced by steel or newer materials.

With the development of the industrial age, and the increased use of iron, the oxidation of iron, or rust, forced the development of steels and the search for new metals and metal coatings to protect surfaces. This gave birth to the science of corrosion control that involves measures of material selection, inhibition, painting, and novel design.

The corrosion of metals is caused by the electrochemical transfer of electrons from one substance (oxygen for example) to another. This may occur from the surfaces of metals in contact, or between a metal and another substance when a moist conductor or electrolyte is present. Depending upon the conditions, various types of corrosion may occur (e.g., general corrosion, intergranular and pitting corrosion, stress corrosion cracking, corrosion fatigue, galvanic and cavitation corrosion, etc.)

Throughout the world, the direct and hidden costs of deterioration due to environmental corrosion amount to billions of dollars per year.

See Also

Atmospheric Chemistry; Atmospheric Pollution; Chemical Bonds and Physical Properties; Chemical Elements; Weathering and Weathering Series