Revealing the mechanism of corrosion products deposition in Cr-coated fuel cladding

Abstract

This study investigates the corrosion and deposition behavior of Cr-coated and uncoated Zr alloys, tested simultaneously under simulated reactor conditions using an internally heated loop system. Results demonstrate that the deposition layers on Cr-coated surfaces are consistently thicker than those on uncoated Zr alloys, with this distinction amplified under higher evaporation rates. At lower evaporation rates, porous layers predominantly composed of Ni(Fe,Cr)₂O₄ nanoparticles form, whereas higher rates lead to a duplex deposit structure with porous outer layers of Ni(Fe,Cr)₂O₄ and dense inner layers of CrOOH and Fe₂O₃. A dissolution-redeposition mechanism is proposed, wherein Cr dissolution produces Cr(VI), later reduced and redeposited as Cr(III) on both Cr-coated and Zr alloy surfaces. Thermodynamic analyses reveal Cr initially integrates into spinel phases (Ni(Fe_1.6Cr_0.4)O₄) until saturation, after which it precipitates as CrOOH. These findings provide insights into corrosion and deposition behavior and the implications of Cr coatings in reactor environments.