Enhanced long-term Pb-Bi corrosion resistance of Y₂O₃-modified FeCrMnAlV coating enabled by self-repairing YBiO₃ layer via V-O-Y bridge bonding

The inherent lack of autonomous self-repairing capability of protective oxide layer limits the long-term service of high-entropy alloys (HEAs) coatings in the Pb-Bi eutectic alloy (LBE) corrosion environment. Herein, this work breaks the limitation by designing a self-repairing oxide layer, which is engineered through the incorporation of V-O-Y bridge bonding in Y₂O₃-modified FeCrMnAlV HEAs coating, where the co-segregation of V element and Y₂O₃ nanoparticles at grain boundaries enables their subsequent cooperative diffusion into the growing oxide layer. Combined experimental and theoretical analyses identify the V-O-Y bridge bonding as a dual-functional unit, which provides highly delocalized electron states to facilitate Y^{3 +} migration and leverages mixed-valence V⁴⁺/⁵⁺ to enhance oxygen reduction kinetics. This synergistic mechanism drives in-situ formation of a dense and stable YBiO₃ self-repairing layer, maintaining exceptional structural integrity over 4000 h of LBE corrosion. The Y₂O₃-modified FeCrMnAlV HEAs coating achieves a record-low parabolic rate constant of 0.00324 μm²/h, which is 1∼2 orders of magnitude lower than currently reported HEAs coatings. Crucially, the scratch test provides further evidence of the complete regeneration of a continuous YBiO₃ layer within 500 h of LBE corrosion, which demonstrates its self-repairing capability. This work establishes a viable design paradigm for developing self-repairing HEAs coatings with exceptional long-term stability against LBE corrosion.