Corrosion Inhibition of Nickel Achieved by Phosphate Addition into Chloride-Rich Media toward Seawater Electrolysis

Mariko Kadowaki; Taku Moronaga; Akiko Nakamura; Yoshiharu Murase; Tomoya Hashimoto; Hideki Katayama; Kazuhiro Takanabe; Yusuke Tsutsumi

doi:10.1021/acs.jpcc.5c04712

Article Corrosion Inhibition of Nickel Achieved by Phosphate Addition into Chloride-Rich Media toward Seawater Electrolysis

Mariko Kadowaki (Research Center for Structural Materials/Materials Evaluation Field/Corrosion Research Group, National Institute for Materials Science) ; Taku Moronaga (Research Network and Facility Services Division/Materials Fabrication and Analysis Platform/Electron Microscopy Unit, National Institute for Materials Science) ; Akiko Nakamura (Research Network and Facility Services Division/Materials Fabrication and Analysis Platform/Electron Microscopy Unit, National Institute for Materials Science) ; Yoshiharu Murase (Research Center for Structural Materials/Materials Evaluation Field/Corrosion Research Group, National Institute for Materials Science) ; Tomoya Hashimoto (Research Center for Structural Materials/Materials Evaluation Field/Corrosion Research Group, National Institute for Materials Science) ; Hideki Katayama (Research Center for Structural Materials/Materials Evaluation Field/Corrosion Research Group, National Institute for Materials Science) ; Kazuhiro Takanabe (Department of Chemical System Engineering, School of Engineering, The University of Tokyo) ; Yusuke Tsutsumi (Research Center for Structural Materials/Materials Evaluation Field/Corrosion Research Group, National Institute for Materials Science)

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Mariko Kadowaki, Taku Moronaga, Akiko Nakamura, Yoshiharu Murase, Tomoya Hashimoto, Hideki Katayama, Kazuhiro Takanabe, Yusuke Tsutsumi. Corrosion Inhibition of Nickel Achieved by Phosphate Addition into Chloride-Rich Media toward Seawater Electrolysis. The Journal of Physical Chemistry C. 2025, 129 (35), 15939-15948. https://doi.org/10.1021/acs.jpcc.5c04712

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Ni-based materials are promising candidates for anodic electrodes and electrolysis cell materials in seawater electrolysis systems for hydrogen production. However, their practical application is hindered by severe corrosion in chloride-rich electrolytes. Incorporating phosphate into the electrolyte has emerged as an effective strategy to enhance corrosion resistance, though the underlying mechanisms remain poorly understood. In this study, the corrosion inhibition mechanism of phosphate on Ni was systematically investigated. Polarization measurements in 0.5 M borate – 0.5 M KCl electrolytes at pH 9.2 with varying phosphate concentrations revealed that Ni undergoes pitting corrosion with Cl−, which is significantly mitigated by phosphate addition. This enhancement is attributed to two factors: 1) structural modification of the passive film, and 2) suppression of pit propagation. STEM/EDS analysis shows phosphate incorporation into the Ni passive film, altering its structure from crystalline to amorphous, which correlates with enhanced protective ability of passive film. Furthermore, potentiostatic polarization reveals that phosphate addition inhibits pit propagation even after its initiation. This inhibition is likely due to the pH buffering effect of phosphate. These findings offer new mechanistic insights into phosphate-assisted corrosion resistance enhancement and provide a foundation for the design of corrosion-resistant nickel-based materials for highly-concentrated chloride environments.

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