Browsing by Author "Oskay, Ceyhun"
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- Corrosion behaviour of FE and NI-based alloys in solar salt and corrosion mitigation strategies via protective coatingsPublication . Oskay, Ceyhun; Meißner, Tobias; Grégoire, Benjamin; Burek, B.O.; Schlereth, Clara; Bonk, Alexander; Bik, Maciej; Solimani, Ali; Galetz, MathiasABSTRACT: 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.
- Dynamic corrosion testing of metals in solar salt for concentrated solar powerPublication . Sutter, Florian; Oskay, Ceyhun; Galetz, Mathias Christian; Cunha Diamantino, Teresa; Pedrosa, Fátima; Figueira, Isabel; Glumm, Stefan; Bonk, Alexander; Aguero, Alina; Rodríguez, Sergio; Reche-Navarro, Tomas Jesus; Caron, SimonABSTRACT: Potassium nitrate and sodium nitrate in mixing proportion of KNO3-NaNO3 40-60 wt% (also called solar salt) has been successfully used for over a decade as heat storage medium for concentrated solar power parabolic-trough collector plants at temperatures up to 400 degrees C. At temperatures of 560 degrees C, reached in state-of-the-art solar tower systems, corrosion of metallic components in contact with solar salt can become an issue and has caused leaks and plant shut-downs in recently built tower projects. While the corrosion rates of several materials have been determined for different temperatures in static molten salt immersion experiments, there is a lack of corrosion data for dynamic in-service conditions. In this work, a dynamic corrosion test has been conducted on 19 different material types including protective coatings, mimicking flow-rate, temperature gradient and draining of inservice operation of a receiver in a concentrated solar power tower. The measured corrosion rates are presented and compared to static corrosion tests reported in literature.