Corrosion behaviour of FE and NI-based alloys in solar salt and corrosion mitigation strategies via protective coatings

ABSTRACT: This study investigated the corrosion behaviour of commercial and model Fe- and Ni-based alloys in solar salt at 600°C. The thermal decomposition of nitrate salts led to an increasing concentration of oxidizing agents in the salt melt and thus to a higher corrosion rate. For Fe-based alloys, the oxide scales contained a Na- and Fe-rich outer layer, followed by an inner Cr-rich layer and nitridation as well as Cr-depletion was observed at the scale/metal interface. Furthermore, higher extent of chloride impurities in solar salt, led to a significantly higher corrosion rate for ferritic-martensitic alloys. For Ni-based alloys, the formation of a duplex scale consisting of a NiO outer and Ni-Cr spinel layer showed protective character during isothermal exposure; however even for Ni-based alloys, Cr was detected in the salt melt, which showed evidence for its dissolution in the melt as toxic hexavalent Cr. Diffusion aluminide and electroless Ni-P coatings deposited on cost-efficient ferriticmartensitic alloys led to formation of protective oxide scales and hindered the Cr-dissolution into the salt melt.

Keywords

Concentrated solar power Molten nitrate corrosion Cr-dissolution Protective coatings

URI

http://hdl.handle.net/10400.9/3936

Citation

Oskay, Ceyhun... [et.al.] - Corrosion behaviour of FE and NI-based alloys in solar salt and corrosion mitigation strategies via protective coatings. In: Livro de Resumos : 8as Jornadas de Corrosão e Proteção de Materiais, Fórum Tecnológico, Lisboa, 24 novembro, 2022, p. 10-15