The precipitation of Ni₃Al reducing the corrosion resistance of alumina-forming austenitic (AFA) steels exposed to 600 °C lead‑bismuth eutectic (LBE) with 10−8 wt% oxygen

This study investigated the corrosion behavior of two AFA steels (Fe-24Ni-15Cr wt%) with 3Al and 4Al, exposed LBE containing 10 −8 wt% oxygen at 600 °C. Unexpectedly, the 4Al steel exhibited much more severe corrosion than the 3Al steel. To explore the anomalous relationship between Al content and corrosion resistance, validation experiments were conducted using advanced high-resolution characterization techniques. The higher Al concentration in the 4Al steel promotes the early precipitation of Ni 3 Al. These Ni 3 Al nanoprecipitates undergo in-situ internal oxidation, forming alumina nanoparticles that inhibit the formation of external protective alumina scales and thereby result in extensive dissolution attack. • Alumina-forming austenitic steels are exposed to Pb Bi with 10 −8 wt% oxygen at 600 °C. • Anomalous corrosion resistance-Al content dependence is revealed. • This anomaly is attributed to the promotion of Ni 3 Al precipitation by higher Al. • Ni 3 Al undergoes in-situ oxidation, inhibiting Al 2 O 3 scale formation.