corrosioninhibitor

A corrosion inhibitor is a chemical substance added in small amounts to a corrosive environment with the aim of reducing the rate at which a metal deteriorates. Inhibitors work by adsorbing onto the metal surface to form protective films, by chemically reacting to create passive surface layers, or by scavenging corrosive species such as oxygen, chloride ions, or hydrogen, thereby altering the electrochemical processes that drive corrosion.

Inhibitors are often categorized by their mechanism and target. Anodic inhibitors primarily slow metal dissolution, cathodic inhibitors slow the reduction reactions at the surface, and mixed inhibitors affect both processes. Organic inhibitors typically rely on heteroatom-containing functional groups (such as nitrogen, sulfur, and oxygen) to adsorb on the surface and create a barrier, while inorganic inhibitors may precipitate protective compounds or modify solution chemistry. Some inhibitors are designed for high-temperature or vapor-phase conditions, and may protect enclosed spaces or systems.

Common types include organic compounds like amines, imidazolines, carboxylates, and benzotriazole derivatives used for steel and copper systems; inorganic inhibitors such as nitrites, phosphates, silicates, and chromates (the latter subject to regulatory restrictions); and vapor-phase inhibitors used in enclosed equipment. Applications span cooling water systems, pipelines, oil and gas production equipment, marine structures, and metalworking fluids, among others.

Evaluation and selection rely on corrosion testing and performance metrics such as polarization resistance, electrochemical impedance spectroscopy, and weight loss. Considerations include effectiveness in the target environment, compatibility with materials and coatings, toxicity, environmental impact, and cost. Regulatory requirements and industry standards (for example, NACE and ASTM guidelines) inform testing and acceptance.