Inhibition of Copper Corrosion by Tolyltriazole in Cooling Systems Using Treated Municipal Wastewater as Makeup Water

Abstract

Tolyltriazole (TTA) has been identified as an effective copper corrosion inhibitor in cooling systems using treated municipal effluent as makeup water. Significant removal of TTA from solution has been reported in previous studies in the presence of free chlorine and copper metal. Hence, for effective dosing of TTA in the cooling systems, it is important to understand the depletion scenario of TTA in solution in the presence of free chlorine and copper metal. In this study, TTA depletion in solution was assessed using batch reactor experiments in the presence of varying concen- trationsoffreechlorineandcoppermetalinsyntheticcooling water simulating treated municipal wastewater. Increasing freechlorineconcentrationresultedinmoredepletionofTTA from solution in the presence of copper metal, which may be due to more adsorption of TTA on to the cuprous oxide sur- face formed with enhanced corrosion of copper metal and to the formation of insoluble copper-TTA complex with the released copper ions in solution. The enhancement of copper metal corrosion in the presence of TTA and increasing con- centration of free chlorine were assessed using electrochem- ical potentiodynamic polarization experiments. Also, TTA adsorption on cuprous oxide surface was assessed in batch reactor experiments. Packing density of TTA on cuprous oxide surface was found to be pH dependent. More TTA was adsorbed onto cuprous oxide surface at higher pH val- ues. Calculations of TTA free energy of adsorption showed that TTA was chemisorbed onto cuprous oxide.