Corrosion Resistance of Alloy 690 in High-Temperature Water with Various Dissolved Hydrogen Concentrations

Scanning electron microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) were used to analyze the oxide film developed on Alloy 690 after being immersed in simulated pressurized water reactor primary water with different dissolved hydrogen (DH) contents. The DH changes the morphology, composition, and thickness of the oxide film on Alloy 690. As the DH level increases, the overall oxide film thickness determined by the O content by XPS to half of its original value decreases, and the thickness of the outer oxide film decreases, with the intersection of Cr content and Fe content lines within the oxide film as the inner/outer layer interface. The thickness of the inner oxide layer at DH = 30 cm³/kg H₂O is similar to that at DH = 50 cm³/kg H₂O but lower than that at DH = 18 cm³/kg H₂O. The Cr content and Cr/(Fe + Ni) ratio in the inner oxide layer increases with the DH level. DH would affect both the chemical compositions of the inner and outer layers and their interface, contributing to the observed oxide film properties from XPS results.