Calgon Corporation

Ann M Cognetti

Jasbir S Gill

John P Pilsits, Jr

A method of use of a composition including either or both isomers of hydrogenated methylbenzotriazole, namely, 5-Methyl-1H-Benzotriazole or 4-Methyl-1H-Benzotriazole which have been at least about 50% hydrogenated, to form corrosion inhibiting films on metal surfaces in an aqueous environment. The hydrogenated methylbenzotriazole compositions provide both improved passivation and improved film persistence when charged to aqueous industrial systems either on a continuous or on an intermittent basis. Continuous dosing is generally kept at a constant &gt;0.5, typically 1-2 ppm in the aqueous system to be treated; intermittent doses are generally 10-20 ppm once every week or two or more. Beyond the improved characteristics described above, films formed from the inventive composition also reduce spiking in corrosion rates immediately following halogen addition; foster faster return to pre-halogenation corrosion rates post-halogenation; and reduce the rate of conversion of phosphonate to orthophosphate, which reduces scale potential. For these reasons, the present compositions are either continuously or intermittently fed and effective to inhibit corrosion of copper and copper alloy surfaces subjected to alkaline, neutral or slightly acidic aqueous systems.

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Pittsburgh, PA, United States of America

Ann M Cognetti