Abstract
Intergranular stress corrosion cracking (IGSCC) and irradiation-assisted stress corrosion cracking (IASCC) been observed at stainless steel components in the primary coolant circuits of boiling water reactors (BWRs) because its corrosive environment .In the past decade, the hydrogen water chemistry (HWC) technique has been widely adopted to protect BWRs’ vessel internal components from IGSCC and IASCC . According to the references, this technique can decrease electrochemical corrosion potential (ECP) of in-vessel components, depress happen ness of SCC, achieve the effects of protecting components’ corrosion. However, the application of HWC is not without problems. The aftereffect is elevated radiation flux when injected higher hydrogen (more than 0.6ppm). The noble metal chemical addition (NMCA) been used to enhance the effectiveness of HWC. The components’ ECP been decided by reduction of oxygen、hydrogen peroxide and the oxidation of metal、hydrogen in the water environment. In this study, measurements of ECP and electrochemical potentiostatic polarization tests in simulated BWR circulation loop to investigate the corrosive behavior of NMCA coating SS 304 (12hr and 24hr coated) at different concentration of O2、H2O2 and H2 in high temperature pure water environment.Test results showed that the oxidative ability of hydrogen peroxide was better than oxygen. In the same concentration, the ECP of specimens in hydrogen peroxide was high than in oxygen, but its corrosive current density in hydrogen peroxide was lower than in oxygen. ECP regards not the only index of SCC susceptibility for BWRs. Various kinetic parameters, such as Tafel slope、exchange current density, and order of reaction were estimated. These parameters are the most crucial factors for the high temperature electrochemistry and the accurate ECP predictive model development for BWR applications.