Benzotriazole and tolyltriazole for cooling-water and yellow-metal corrosion control
Copper and brass passivation in open recirculating and closed-loop cooling systems, with the form and chemistry matched to your water.
Copper and brass passivation in open recirculating and closed-loop cooling systems, with the form and chemistry matched to your water.
A copper corrosion inhibitor is the azole component of a cooling-water treatment program. Cooling systems run copper and brass through tubing, heat-exchanger bundles, and fittings. Left untreated, those yellow metals corrode in recirculating water, and the dissolved copper that comes off them plates onto steel downstream and drives galvanic attack across the system. Benzotriazole and tolyltriazole are the standard inhibitors that stop this; which one, and at what residual, is in azole inhibitors for copper and brass in cooling water.
Benzotriazole and tolyltriazole bond to the copper surface and build a thin protective film. On copper, the inhibitor reacts with surface copper ions to form an insoluble copper-azole layer that holds as a barrier. The film blocks chloride, sulfate, and dissolved oxygen from reaching the metal, and it works at very low dose rates. The surface ends up passivated, which means it resists pitting and stops shedding copper into the water.
Because the film suppresses copper dissolution, it also protects the rest of the system. Less copper in the water means less copper plating onto mild steel, which means less of the galvanic corrosion that copper ions would otherwise set off.
Both inhibitors passivate yellow metal. The water decides which one fits.
Benzotriazole is a straightforward choice for mild, stable, closed-loop systems where conditions stay non-aggressive. It dissolves cleanly and protects well when the chemistry is not fighting an oxidizer. Tolyltriazole is the more durable choice when the system runs hot or carries chlorine. The methyl group on the ring gives tolyltriazole better thermal stability and better resistance to chlorine and other halogen biocides, so it keeps protecting in open recirculating towers under active chlorination and in higher-temperature loops where benzotriazole would degrade faster. For systems that need both microbial control and steady metal protection, tolyltriazole is usually the safer pick.
Both inhibitors come as a solid 99% granular and as a sodium-salt liquid. Water-treatment programs that meter a liquid feed often run sodium benzotriazole 40% or sodium tolyltriazole 50%, which are supplied water-soluble and ready to dose. Formulators who build their own concentrate, or who add inhibitor to a dry blend, often take the solid granular: benzotriazole fine granular 99% or tolyltriazole granular 99%. The active chemistry is identical. See the corrosion inhibitors page for the full breakdown of forms and pack sizes.
P.A.T. Products supplies benzotriazole and tolyltriazole in both forms across the United States, Canada, and Mexico. TDS, SDS, and a Certificate of Analysis per lot are available, with REACH statements on request. Each grade page in the corrosion inhibitor catalog carries the specification the material is released against and the documents that come with it. Tell us your water and your feed method, and we will recommend a product, a form, and a pack size, and send a sample.
Tolyltriazole. Its methyl group gives it better resistance to chlorine and other halogen biocides and better thermal stability, so it keeps protecting copper in open recirculating towers under active chlorination, where benzotriazole would degrade faster.
When copper corrodes, it releases copper ions into the water. Those ions plate onto mild steel downstream and form a galvanic couple that corrodes the steel quickly. By stopping copper from dissolving, the inhibitor keeps copper ions out of the water, which reduces the copper plating and the galvanic attack on the steel.
Programs that meter a liquid feed usually run the sodium-salt liquid, supplied ready to dose. Programs that make up their own concentrate often take the solid 99% granular and dissolve it. The chemistry on the metal is the same.