Study On The Corrosion Inhibition Mechanism And Efficiency Of Component Cooling System (CCS) Inhibitors

In nuclear power plants, Component Cooling System (CCS) is a must, providingcooling to safety-related and non-safety-related systems. Corrosion and fouling ofheat exchangers could largely decrease their efficiency, causes piping blocking,sometime even shut down of plants. Therefore, it is necessary to attach highimportance to corrosion of CCS. In many cases, corrosion inhibitor is used to mitigatethis problem because of its advantages such as convenient operation, instant effectand being able to protect the whole system.The main construction material of CCS is carbon steel and copper. First,potentiadynamic polarization and EIS are used to study the inhibition of carbon steelby NaNO2and Na2MoO4and their compounds. Then, immersion test,potentiadynamic polarization, EIS,SEM and XRD are used to study the corrosionbehavior of red copper and brass in solutions of700ppmNaNO2、2.0ppm Cl－+3.0ppm NH3+700ppm NaNO2+10ppm TTA、520ppmNa3PO4.It shows that:1. Both NaNO2and Na2MoO4are anodic corrosion inhibitors. The inhibitionefficiency (IE) of NaNO2reaches up to98.9%, Na2MoO4up to97.9%.2. An obvious synergistic effect happens between206mg/L Na2MoO4and75mg/LNaNO2,which is the optimal compound, considering engineering factors andeconomical factors.3. Electrode reaction is mainly controlled by charge transfer in blank solution. Thediffusion at low frequencies contributes to the rapid formation of a porous layer.In solution containing NaNO2and Na2MoO4, mass transfer by diffusion controlsthe reaction process.4. TTA is a cathodic corrosion inhibitor. IE of1ppm NaNO2is up to91.3%, and itincreases with the concentration. Besides, Cl-and NH3does not have notableeffect on the IE.5. Na3PO4is more corrosive to red copper than NaNO2, and cannot be used ascorrosion inhibitor for copper.