A novel kinetic model for dissolution and precipitation of oxide on stainless-steel surface in stagnant liquid sodium

This study presents sodium experiments and a novel kinetic model to elucidate the dissolution and precipitation behavior of oxides on the stainless-steel (SS) surface in stagnant liquid sodium. Experiment results demonstrated that the oxygen from Na₄FeO₃ on the SS surface dissolved into the liquid sodium at a rate of $v_{dis}\approx 9.3\times {10}^{-5}$ wt.ratio/h within 20 h. Subsequently, oxide precipitation occurred on the SS surface at a rate of $v_{pre}\approx 1.4\times {10}^{-5}$ wt.ratio/h. To further investigate the precipitation dynamics, a phase-field (PF) simulation code was developed, enabling sensitivity analyses of six parameters: temperature ($T$), initial oxygen concentration ($c_0$), interfacial energy ($\gamma$), oxygen diffusion coefficient ($D_L$), quasi-partition coefficient ($k$), and time step ($\Delta t$). The PF simulations revealed that the precipitation rate increases linearly with $c_0$ and $D_L$. In contrast, it decreases exponentially with increasing $T$ and $\gamma$. The parameters $k$ and $\Delta t$ exhibited negligible influence on the calculation results. Notably, the oxide precipitation rates obtained by the PF calculation show consistency with the laboratory-scale experimental findings reported by LatgÉ et al, supporting the model’s validity.