Effect of Silicon and Aluminum Addition on Corrosion Behavior of ODS Iron-Based Alloys in Liquid Lead–Bismuth Eutectic

The long-term corrosion behaviors of four variants of oxide dispersion strengthened (ODS) iron-based alloys in the stagnant oxygen-saturated lead–bismuth eutectic (LBE) at 550 °C were studied herein. The effects of silicon and aluminum content on the thickness, morphology and composition of the oxide scale were explored with the aid of X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe micro-analyzer (EPMA) and X-ray photoelectron spectroscopy (XPS). The addition of 1.5 wt% silicon is not able to contribute to forming a protective external silicon oxide film on the surface of aluminum-free ODS iron-based alloy, while the addition of aluminum promotes the formation of a thin and continuous alumina oxide scale. In the meantime, an appropriate amount of silicon becomes the heterogeneous nucleation site for alumina during the initial stage of oxidation, giving rise to the rapid formation of a protective alumina scale. However, excessive silicon has a negative impact on the formation of continuous alumina scale, because it may compete with aluminum to absorb more oxygen. The result of oxidation kinetics in ODS iron-based alloy shows that the parabolic rate constant of the alumina oxide scale is 3–4 orders of magnitude lower than that of the scale mainly composed of iron and chromium oxide.