Benzotriazole

Benzotriazole is an organic compound with the formula C6H5N3. It is a white crystalline solid that consists of a benzene ring fused to a triazole ring, giving the benzotriazole system. The most common isomer is 1H-benzotriazole. In chemical terms, the molecule has several nitrogen atoms capable of donation, which allows it to act as a ligand and as a protective film former on metal surfaces.

It is widely used as a corrosion inhibitor for copper and its alloys in cooling circuits, desalination plants, and lubricants. When adsorbed onto copper surfaces, benzotriazole forms a protective layer that slows metal dissolution and dezincification. Related derivatives, such as tolyltriazole, are also used for similar corrosion protection, often with different solubility or compatibility properties. In addition, benzotriazole derivatives serve as ultraviolet absorbers in polymers and coatings.

Mechanistically, BTA coordinates to copper via its nitrogen sites, creating a barrier against aggressive ions. The protective film reduces the cathodic and anodic reactions that drive corrosion. Its effectiveness depends on pH, temperature, and the presence of other ions and organic species.

Benzotriazole is sparingly soluble in water and more soluble in many organic solvents. It is relatively thermally stable and can be used at elevated temperatures in industrial formulations.

Safety and environmental considerations include potential irritation on contact with skin or eyes and aquatic toxicity at sufficient concentrations. Handling requires appropriate protective equipment. In the environment, BTA can persist and is monitored in some wastewater and surface-water programs; removal is achieved by adsorption, advanced oxidation, or precipitation in some cases.

See also: tollyltriazole and other benzotriazole family inhibitors.