Work

Effects of Zn and Ni addition on the Co incorporation in 316 SS oxide formed under simulated BWR conditions

Year: 2025

Type: article

Abstract: A critical insight into how Co incorporation in the oxide formed on 316 Stainless Steel (SS) in simulated Boiling Water Reactor (BWR) conditions is influenced by the presence of Zn and/or Ni injected in the water was revealed through advanced microstructural/microchemical analyses. The experiments involved exposing coupons of 316 SS to multistage oxidation tests under low-level Hydrogen Water Chemistry (HWC) (H:O molar ratio ∼8) at 288 °C, both in the absence and the presence of metal cations injection (Zn, Ni, Co). Moreover, Online NobleChem™ (OLNC) was applied in an intermediate exposure stage on pre-oxidised coupons to show how the transition from a non-catalytic to a catalytic oxide surface impacts the oxide properties. The application of OLNC did not substantially influence the incorporation of metal cations in the oxide. Notably, the study showed that Co was preferentially incorporated into the normal spinel oxides, thus suggesting that Co2+ prefers the tetrahedral sites of these spinel, similar to Zn2+. This translated into a Co uptake mitigation effect when 10 ppb of Zn was injected. Conversely, in the presence of 10 ppb of Ni in the water, Co uptake was not mitigated, suggesting that Ni2+ does not compete with Co2+ for the same interstitial sites of the spinel oxides. However, a mitigation effect on Co uptake was observed when Zn and Ni were injected simultaneously, indicating a synergistic effect of these metal cations on the Co incorporation mechanism.

Source: Corrosion Science

DOI: 10.1016/j.corsci.2025.113023