corrosivity

Corrosivity refers to the tendency of a substance to cause damage to materials, especially metals, through chemical or electrochemical reactions. A corrosive substance can remove material, alter its structure, or weaken it, often leading to failure if exposure is sustained. Corrosivity depends on both the substance and the material it contacts, as well as conditions such as temperature and moisture.

Factors that influence corrosivity include the substance’s chemical composition, concentration, temperature, exposure time, presence of water or humidity, oxygen levels, pH, conductivity, and whether a protective surface film exists. Aggressive environments, high temperatures, and conductive solutions typically increase corrosion rates.

Corrosion manifests in several forms. Uniform corrosion causes even material loss over a surface, while localized forms such as pitting, crevice corrosion, galvanic corrosion, and intergranular corrosion create small or concentrated damage. Galvanic corrosion occurs when two dissimilar metals are in contact in the presence of an electrolyte. Corrosivity is often assessed by measuring corrosion rate, typically expressed as millimeters per year (mm/year) or equivalent weight loss in standardized tests.

Common corrosive agents include strong acids and alkalis, oxidizers, chlorides, and certain industrial cleaners. Environmental factors such as atmospheric pollution, seawater exposure, and battery or process fluids contribute to corrosive conditions. Standards and tests, such as salt spray testing and electrochemical methods, are used to evaluate materials' resistance and to compare corrosivity of environments.

Prevention and mitigation focus on material selection, protective coatings and surface treatments, cathodic protection, inhibitors, and design practices that minimize crevices, leaks, and galvanic coupling. Handling and storage of corrosive substances require appropriate safety measures, including labeling, containment, ventilation, and personal protective equipment.