Second Generation, Halogen Resistant Copper Corrosion Inhibitors

Abstract Copper alloys are utilized in industrial cooling systems because of their excellent heat transfer properties. However, a corrosion inhibitor is needed to prevent equipment failures and, very importantly, to reduce the discharge of toxic copper compounds into the environment. Azoles, such as benzotriazole (BZT) and tolyltriazole (TTA), have been used for this purpose but they do not protect copper in the presence of oxidizing halogens which are commonly added to cooling systems to control microbiological activity. The halogens react with BZT and TTA and destroy their corrosion inhibiting properties. Recently, an azole derivative was discovered which was much less susceptible to degradation by oxidizing halogens. In the present paper, continuing work toward the development of improved copper corrosion inhibitors is discussed. Several new copper corrosion inhibitors have been discovered which are extremely resistant to reaction with chlorine. In simulated cooling water conditions, these inhibitors provide outstanding copper corrosion inhibition when chlorine is present. The improved copper protection eliminates pitting corrosion of mild steel, which is a consequence of the breakdown of copper protection in chlorinated, mixed metal systems. One of the compounds, 5-benzyl-benzotriazole, forms particularly stable films on copper. This material provides excellent film persistence when applied in a shot feed mode. Data are presented for both fresh water and sea water.