Corrosion rates measured under potentiostatic conditions to represent performance of a cermet nuclear waste form

ABSTRACTElectrochemical tests were conducted to assess the corrosion performance of a developmental multiphase cermet nuclear waste form in different conditions. Corrosion currents were monitored as the surface equilibrated in an acidic brine solution during potentiostatic tests at different imposed potentials. Electrochemical impedance spectroscopy was used to quantify differences in the electrical properties of surfaces stabilised at different potentials. The passivating oxides that will stabilise the surface under disposal conditions are formed and maintained during testing. The measured corrosion currents were two orders of magnitude lower for passivated surfaces than for polished surfaces over a wide range of redox conditions. The electrochemical results were correlated with microscopic analyses of the corroded surfaces and physical models of the surface passivation and degradation processes are proposed. The measured corrosion rates are suitable for the long-term performance modeling of cermet nuclear waste forms.KEYWORDS: Stainless steelintermetallicsacid solutionspotentiostaticelectrochemical impedance spectroscopy (EIS)scanning electron microscopy (SEM)passive filmsPourbaix diagram AcknowledgementsThis work was funded under DOE Nuclear Energy University Program Grant DE-NE-IL-UIC-0203-02. Work conducted at Argonne National Laboratory is supported by the U.S. Department of Energy, Office of Nuclear Energy, under Contract DE-AC02-06CH11357. The authors acknowledge Drs. Terry A. Cruse and Jeffrey A. Fortner for technical discussions and assistance with the microscopy.Disclosure statementNo potential conflict of interest was reported by the author(s).Data availability statementThe raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.CRediT authorship contribution statementV.K. Gattu: Conceptualization, Methodology, Experiment, Data curation, Visualization, Writing – reviewing and editing, W.L. Ebert: Methodology, Resources, Project administration, Writing – review & editing, J.E. Indacochea: Funding acquisition, Methodology, Supervision, Project administration, Writing – review & editing.Declaration of competing interestThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.Additional informationFundingThis work was supported by Nuclear Energy University Program: [Grant Number DE-NE-IL-UIC-0203-02].