Abstract
Abstract Incidents of intergranular stress corrosion cracking (IGSCC) and irradiation-assisted stress corrosion cracking (IASCC) of stainless steel components in the primary coolant circuits of boiling water reactors (BWRs) are occurring with increasing frequency as the power reactors age. In the past decade, the hydrogen water chemistry (HWC) technique has been widely studied as a measure for mitigating IGSCC and IASCC in BWR vessel internal components. However, this technique is not without problems. In general, at a feedwater hydrogen concentration higher than 0.6 ppm, the radioactive Nitrogen-16 content in the main steam line is very likely to increase and the resulting radiation fields exert a high man-REM cost on the operator. Furthermore, it is not at all clear that HWC is effective in protecting some components against IGSCC and IASCC in terms of electrochemical corrosion potential (ECP) reduction, particularly for protecting near-core components. Therefore, new technologies, such as inhibitive coatings, were brought into consideration to enhance the effectiveness of HWC in the aspects of lower hydrogen consumption and more effective ECP reduction. In the current study, surfaces of pre-oxidized Type 304 stainless steels (SS) were treated with various chemical compounds of TiO2, ZrO2, and ZrO(NO3)2 by chemical immersion at different temperatures. Electrochemical potentiodynamic polarization, ECP measurement, and slow strain rate tensile (SSRT) test were conducted to characterize the corrosion properties of the treated and untreated stainless steels. Test results showed that the treated SS specimens exhibited lower open circuit potentials, corrosion densities, and passive current densities than the untreated（pre-oxidized only）specimens. The ECPs of the treated and untreated specimens at 288 oC could vary by more than 200 mV at different dissolved oxygen concentrations, and the pre-oxidized specimen did not exhibit the highest ECP. According to the SSRT test results, all tested specimens showed severe IGSCC, but the pre-oxidized one had the lowest elongation and the shortest fracture time.