Online monitoring of copper corrosion inhibitors in cooling water

Importance of the Topic

Monitoring copper corrosion inhibitors in cooling water is critical for industrial heat‐exchange systems. Copper and its alloys deliver high thermal efficiency but are vulnerable to corrosion, which leads to equipment failures, unplanned downtime, and reduced heat‐transfer performance due to fouling. Dissolved copper also poses environmental hazards and promotes galvanic corrosion on steel surfaces. Effective online monitoring of inhibitor levels helps maintain system integrity, optimize chemical dosing, and ensure compliance with discharge limits.

Objectives and Study Overview

This work presents an automated approach for the continuous determination of triazole-based corrosion inhibitors in power‐plant cooling water. The goal is to provide real‐time data on inhibitor concentrations—specifically benzotriazole, tolyltriazole, and 2-mercaptobenzothiazole—to prevent metal degradation, minimize chemical waste, and support trend analysis for proactive maintenance.

Methodology and Instrumentation

The analytical method employs ion chromatography with direct UV/VIS detection at 214 nm. Samples are drawn continuously from a bypass line and conditioned automatically. Key steps include:

• Inline sample filtration and dilution
• Automated eluent preparation to ensure stable baselines
• Separation on an IC column optimized for aromatic adsorption
• Quantification using UV detection for trace‐level sensitivity

Used Instrumentation

The analysis is performed with a Metrohm 2060 IC Process Analyzer featuring:

• Modular architecture to support up to 20 sample streams
• Continuous eluent production module and optional PURELAB® flex for ultrapure water
• Multiple detector blocks including UV/VIS and conductivity
• All-in-one software for method scheduling, trend analysis, and process communication (Modbus/Discrete I/O)

Main Results and Discussion

Chromatograms of spiked cooling‐water samples (1 mg/L each triazole) demonstrated clear resolution and low baseline noise. Automated calibration yielded low detection limits (sub-mg/L), excellent reproducibility (RSD <2 %), and high recovery rates. The system ran continuously with minimal maintenance, and level sensors provided advance notice of reagent replacement. Conductivity channels complemented UV data to track general water chemistry shifts.

Benefits and Practical Applications

The online IC method offers multiple advantages:

• Real‐time inhibitor monitoring for optimized dosing
• Reduced chemical consumption and operational costs
• Enhanced equipment protection and extended maintenance intervals
• Automated alarms and feedback to process control systems
• Compliance with environmental discharge regulations

Future Trends and Applications

Advances in sensor integration, data analytics, and predictive maintenance will further improve corrosion control. Combining IC data with machine-learning algorithms could forecast inhibitor depletion and corrosion risk. Expanding multi-stream monitoring and integrating additional analytes—such as dissolved oxygen or metal ions—will provide a comprehensive water‐chemistry profile for smarter plant management.

Conclusion

The automated ion chromatographic determination of copper corrosion inhibitors enables reliable, high-throughput monitoring in cooling‐water systems. The Metrohm 2060 IC Process Analyzer ensures consistent performance, reduces manual intervention, and supports proactive maintenance strategies that protect equipment, lower costs, and safeguard the environment.

Reference

1. AN-U-060 Corrosion inhibitors in cooling water
2. AN-PAN-1042 Online trace analysis of anions in the primary circuit of nuclear power plants
3. AN-PAN-1043 Online trace analysis of cations in the primary circuit of nuclear power plants
4. AN-PAN-1044 Online trace analysis of amines in the water steam circuit of power plants