Corrosion

Corrosion is the deterioration of materials, especially metals, due to chemical or electrochemical reactions with the environment. It often results in material loss, diminished strength, and sometimes failure. The most familiar example is iron rusting: iron reacts with water and oxygen to form oxides. Corrosion is driven by the thermodynamic tendency of refined metals to return to more stable compounds.

Most metal corrosion is electrochemical: metal surfaces act as anodes or cathodes in an electrolyte, with electrons flowing through the metal and ions moving in the liquid. Localized forms include pitting, crevice corrosion, intergranular corrosion, and stress corrosion cracking, while uniform corrosion affects large areas. Some metals passivate briefly, forming protective oxide films; others corrode aggressively in certain environments.

Factors influencing corrosion include environment (moisture, temperature, pH, salinity, pollutants), metal or alloy composition, surface condition, and presence of protective coatings or inhibitors. Dissimilar metals in contact can cause galvanic corrosion, and restricted flow in crevices or deposits can accelerate it. Concrete structures may suffer reinforcement corrosion due to carbonation or chloride ingress.

Prevention and control strategies aim to slow or stop corrosion. They include protective coatings and platings, cathodic protection (sacrificial anodes or impressed current), corrosion inhibitors, and selecting corrosion-resistant materials. Proper design reduces crevices and moisture retention. Regular inspection, corrosion monitoring, and non-destructive testing are used to assess rates and plan maintenance.

Corrosion science and engineering study these processes to extend service life and reduce costs in industries such as construction, energy, and transportation. Understanding corrosion mechanisms and applying appropriate control measures are essential for safety, reliability, and sustainability.