Effects of water chemistry on corrosion and plugging in the copper heat exchangers of water-cooled generators in power plants

Corrosion and plugging of hollow copper conductors in water-cooled generators can cause system failures, such as flow restrictions and forced unit outages. Although both neutral water chemistry (NWC) and slightly alkaline water chemistry (SAWC) have been proposed as solutions, field operations show that NWC frequently suffers from system failures, while SAWC demonstrates high reliability. The scientific basis for this phenomenon has not been well understood. In this paper, the thermodynamics of NWC and SAWC were established to compare their tendencies toward copper corrosion and plugging. SAWC keeps copper in a stable CuO passivation region, exhibiting a superior buffer capacity against CO2 2 inleakage and the temperature rise of the cooling water. This buffer capacity is further enhanced by increasing the degree of the slight-alkalization. Under the SAWC with a pH value of 9.0 at 298.15 K, the concentration of the dissolved copper species is extremely low, and the positive temperature coefficient of CuO solubility prevents the accumulation of copper corrosion products in high- temperature regions. In contrast, NWC is susceptible to corrosion and plugging due to its poor buffer capacity. This study provides new insights into the effects of water chemistry on copper corrosion and plugging from a thermodynamic perspective, offering a sound theoretical basis for field operations.