When used as a disinfectant in industrial circulating water systems, TCC powder's strong oxidizing and chlorinating properties may pose a corrosion risk to metal equipment. However, scientific management can achieve a balance between effective disinfection and corrosion prevention. The hypochlorous acid and active chlorine produced by TCC powder upon dissolution in water are the core bactericidal agents. However, the synergistic effect of chloride ions and dissolved oxygen can accelerate electrochemical corrosion of metals, particularly in high-temperature and high-flow environments, leading to localized damage such as pitting and crevice corrosion. Therefore, a multi-faceted anti-corrosion system must be developed, encompassing water quality control, optimized dosing methods, and the coordinated use of corrosion inhibitors.
Precise control of water quality parameters is fundamental to corrosion prevention. The pH of the circulating water must be maintained within a slightly alkaline range. The addition of alkaline agents such as sodium hydroxide or sodium carbonate can neutralize the acidic substances produced by the hydrolysis of TCC powder and inhibit hydrogen ion attack on metals. Dissolved oxygen levels must also be strictly controlled, using vacuum deaerators or chemical deoxidizers such as sodium sulfite to reduce potential corrosion caused by oxygen concentration gradients. Furthermore, reducing suspended solids concentration through a side filtration system and preventing impurities from depositing on metal surfaces and forming oxygen concentration gradients are also key measures for preventing under-scale corrosion.
Optimizing the dosing method directly impacts the effectiveness of corrosion protection. Continuous dosing, rather than intermittent dosing, maintains a more stable residual chlorine concentration, reducing the repeated formation and shedding of protective films on metal surfaces caused by concentration fluctuations. Practice at the Beijing Energy Thermal Power Plant has demonstrated that by controlling the dosing frequency and single-dose dosage of trichloroisocyanuric acid powder using a pulse dosing method, residual chlorine values can be stabilized within a safe range, ensuring sterilization efficiency while reducing corrosion risks. For large circulating water systems, it is recommended to equip them with automatic dosing devices that adjust the dosage in real time based on online water quality monitoring data to avoid operational errors.
The coordinated use of corrosion inhibitors is an effective method for directly protecting metal equipment. For carbon steel equipment, oxide film-forming corrosion inhibitors such as chromates and molybdates can be used to form a dense passivation layer on the metal surface. For copper alloy equipment, benzotriazole-based adsorption film-forming corrosion inhibitors can block chloride ion contact through molecular adsorption. Composite corrosion inhibitors are more commonly used. Their zinc ions, polyphosphates, and other ingredients work synergistically to create a multi-layered protective structure on metal surfaces. Care should be taken to ensure compatibility between the corrosion inhibitor and TCC powder to avoid chemical reactions that could weaken the efficacy.
Microbial control and corrosion prevention have a synergistic effect. The bactericidal effect of TCC powder can reduce the growth of corrosive microorganisms such as sulfate-reducing bacteria. The hydrogen sulfide produced by their metabolism is a key agent that exacerbates metal corrosion. Maintaining an appropriate residual chlorine level not only controls the total microbial population but also disrupts the biofilm structure, preventing the combined effects of microbial and electrochemical corrosion. However, excessive chlorine dosage should be avoided, as it can lead to the accumulation of microbial debris and the formation of corrosive deposits. Therefore, regular monitoring of microbial indicators and adjustment of dosage levels are necessary.
Equipment material selection and maintenance are also critical. During system design, chlorine-resistant materials should be selected based on water quality conditions. For example, copper alloy heat exchangers require controlled chloride ion concentrations, while carbon steel equipment requires maintaining a pH above a certain level. Regular inspections should be implemented during operation to assess equipment corrosion using techniques such as ultrasonic thickness measurement and electrochemical impedance spectroscopy, allowing for the timely replacement of severely corroded components. Equipment that is out of service should be thoroughly cleaned and kept dry, or nitrogen-filled to prevent corrosion during downtime.
Process optimization can indirectly reduce corrosion risks. In circulating water systems, avoid drastic fluctuations in TCC powder concentration. Continuous dosing should be used to maintain a stable residual chlorine level to prevent localized excessive concentrations from causing the protective film on metal surfaces to fall off. The circulating water flow rate should also be controlled within a reasonable range. Excessive flow rates can erode and destroy the protective film formed by the corrosion inhibitor, while excessively low flow rates can easily cause deposits to accumulate. For critical equipment, localized anti-corrosion measures can be upgraded, such as applying chlorine-resistant coatings such as epoxy resins and polyurea.
