Abstract
The structural materials in nuclear power plants experience corrosion under high temperature water chemistry environments, which could result in serious safety issues. Zinc injection to the primary side chemistry has been demonstrated to reduce corrosion rate of the structural materials and radiation dose rate by modifying the oxide film formed on the structural materials. The purpose of this work is to investigate the effect of Zn addition at different concentrations on 304SS under PWR primary side conditions by SEM, GIXRD, Raman spectrum, XPS, electrochemical method and thermodynamic calculation. When Zn concentration is increased, the number and size of Fe-based spinel oxide particles in the outer layer decreases while Cr-based spinel oxide in the inner layer remains unchanged. The corrosion current density of 304SS and defect density of the oxide film decrease with increasing Zn concentration. These results conclude that corrosion resistance of 304SS is enhanced in the presence of Zn. In addition, the thermodynamic analyses on the spinel oxides of surface were performed and the results are in good agreement with the experimental observations presented in this work.
Highlights
The structural materials, such as stainless steel (SS) and Ni-based alloys, used in nuclear power plants (NPPs) have demonstrated excellent performance against corrosion
The oxide films formed on the structural materials in the aqueous environment have a duplex structure, which typically comprises of an inner layer of Cr-rich oxides and an outer layer of Fe-rich oxides (Sennour et al, 2010; Liu et al, 2014)
It has been widely though that large oxide particles are located in the outer layer of the oxide film and small oxide particles in the inner layer
Summary
The structural materials, such as stainless steel (SS) and Ni-based alloys, used in nuclear power plants (NPPs) have demonstrated excellent performance against corrosion This is due to formation of a protective oxide layer on the surfaces can effectively separate the underlying alloy from the surrounding environment and protect the alloy from corrosion (Lu et al, 2009; Pandey et al, 2009; Hoffelner, 2013; Chen et al, 2019; Yang et al, 2021; Wang et al, 2022). When these structural materials are exposed to the aggressive environments, such as the high temperature, water chemistry and high stress, the oxide layer can be damaged, leading to occurrence of localized corrosion (Landolt, 2007). Kawamura et al (1998) and Ziemniak and Hanson (2005) revealed that when Zn2+ was present at 10 ppb or higher, the outer
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