Nano-scale evidence for coupled interfacial dissolution-reprecipitation (CDR) controlling corrosion of alumina-forming austenitic (AFA) steel in static lead-bismuth eutectic (LBE) at 600°C

Abstract

Despite extensive research on dissolution corrosion, whether element dissolution is selective or non-selective remains unclear, due to limitations of past characterization technologies. Using nano-scale characterization, we investigated AFA steel exposed to LBE with 10⁻⁸ wt.% oxygen at 600°C for 1700 h, found that alloying elements dissolve non-selectively into LBE and then reprecipitate, forming penetrable corrosion zone that inherits substrate crystallographic information and comprises ferrite, river-like NiAl, and NiAl nanoparticles. The ferrite and river-like NiAl exhibit complete elemental segregation due to liquid-phase diffusion, while NiAl nanoparticles form via reaction-diffusion. This supports that coupled dissolution-reprecipitation mechanism primarily controls dissolution corrosion at 600°C.