*2.1. Materials*

A Fe-Cr-Zr alloy with a weight of 10 kg is produced by vacuum induction melting technique, and the chemical composition is given in Table 1. The ingot is hot forged and then hot rolled to ~12 mm thick plate. The plate is annealed at 1373 K for 15 min followed by air cooling.

**Table 1.** Chemical compositions of Fe-Cr-Zr alloy.


#### *2.2. Oxidation Tests in Air and in Liquid Pb-Bi Eutectic*

Samples with dimensions of 8 mm × 8 mm × 8 mm are ground with SiC abrasive papers up to 2000 grit, mechanically polished with 0.5 μm diamond powder, and ultrasonically cleaned by ethanol prior to oxidation tests. The oxidation behaviors in air are evaluated by continuous isothermal oxidation tests, which are conducted at 923 K for different durations up to 1000 h in a furnace with stagnant air. The weight measurement for evaluating the oxidation rate is performed by using a Sartorius BP211D electric balance (Sartorius, Goettingen, Germany) with an accuracy of 0.01 mg.

Furthermore, the oxidation behaviors in liquid metal are evaluated by the isothermal oxidation tests in oxygen-saturated stagnant liquid Pb-Bi eutectic at 823 K using a selfdeveloped liquid Pb-Bi eutectic corrosion test apparatus [19,20]. Ar + 5% O2 serves as the cover gas to ensure the oxygen-saturated condition and avoid excessive oxidation of the liquid Pb-Bi eutectic. The presence of thin PbO on the liquid metal surface indicated that liquid Pb-Bi eutectic is oxygen-saturated. The samples are taken out after immersion in the oxygen-saturated Pb-Bi eutectic for 500 h, 1000 h, and 2000 h, respectively.
