Probing High-Temperature Electrochemical Corrosion of 316 Stainless Steel in Molten Nitrate Salt for Concentrated Solar Power Plants

• Published in: Journal of materials engineering and performance Vol. 31; no. 6; pp. 4902 - 4908
• Main Authors: Singh, Mahander Pratap, Basu, Bikramjit, Chattopadhyay, Kamanio
• Format: Journal Article
• Language: English
• Published: New York Springer US 2022
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Corrosion and Coatings; Engineering Design; Materials Science; Quality Control; Reliability; Safety and Risk; Technical Article; Tribology; concentrated solar power; corrosion; electrochemical impedance spectroscopy; solar salt; 316-stainless steel
• ISSN: 1059-9495; 1544-1024
• DOI: 10.1007/s11665-021-06538-x

The corrosion resistance of structural materials, particularly in molten salt environments, is of central importance to design concentrated solar power (CSP) plants. In this perspective, the high-temperature electrochemical behavior of passive film on 316SS in solar salt composition (60 pct. NaNO
3
: 40 pct. KNO
3
by wt. pct.) was evaluated using linear resistance polarization, Tafel polarization, and electrochemical impedance spectroscopy techniques in the application range of 400 to 550 °C. An increase in corrosion rate with temperature and severe oxidation at 550 °C was recorded. However, the corrosion potential (E
corr
) does not vary significantly. The critical analysis of the impedance bode phase diagram reveals two well-separated maxima at 400 °C, indicating the role of the passive layer during the corrosion process. At 500 °C, the observed phase angle is close to 45°, attributed to processes controlled by mass transfer limitations. While analyzing the influence of mass transfer, an equivalent circuit model has been proposed to analyze the corrosion of the 316SS, a material used for piping and containment of CSP plants in molten solar salt.