Corrosion Behavior of Two Gd Particle-Doped Fe-Based Amorphous Coatings with Excellent Neutron Absorption Performance

Safe long-term storage of spent nuclear fuel requires materials that combine high neutron absorption with excellent corrosion resistance. In this study, two Gd-doped Fe-based amorphous coatings (2X5 + Gd and PC + Gd) containing 6.0 wt.% Gd were fabricated by high-velocity air–fuel (HVAF) spraying. The coatings exhibit macroscopic neutron absorption cross-sections 16.8 and 15.8 times that of borated stainless steel with a B content of 0.6 wt.%, respectively. Electrochemically, both coatings show spontaneous passivation and superior localized corrosion resistance, with PC + Gd outperforming 2X5 + Gd due to a Cr2O3-enriched passive film facilitated by P addition. A unique “dissolution–passivation” mechanism governs corrosion: Gd particles dissolve preferentially as anodes, while the amorphous matrix rapidly repassivates, ensuring durable protection. This work provides a viable strategy for designing high-performance neutron-absorbing composite coatings.