Online corrosion monitoring system for thermal storage tanks using molten salts. Laboratory scale-up to demonstration parabolic-trough plant

• Main Authors: Pérez, Francisco Javier, Miguel, María Teresa de, Encinas-Sánchez, Víctor, Lasanta, María Isabel, Illana, Andrea, García-Martín, Gustavo
• Format: Conference Proceeding
• Language: English
• Subjects: Corrosion; Corrosion mechanisms; Corrosion potential; Corrosion rate; Corrosion tests; Ion transport; Laboratories; Molten salts; Monitoring; Monitoring systems; Power plants; Stainless steels; Storage tanks; Thermal storage
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/5.0028939

This research aims to assess and monitor the corrosion of 321H stainless steel in a quaternary salt mixture that consist of the Hitec salt, to which a 1%wt. of LiNO3 is added. Assessment and monitoring of the steel was carried out by an online two-electrode system that enables electrochemical impedance measurements in real-time. The system was initially developed for laboratory analysis and then scaled up to a demonstration parabolic-trough plant. Results obtained at lab-scale indicated that corrosion in 321H steel is controlled by ion transport in the scale, providing a corrosion rate of 8.87 µm·year-1. Lab results were validated by conventional lab-scale characterization techniques, which after 1000 h of testing showed a corrosion layer mainly constituted by Fe2O3 and FeCr2O4. Results at plant-scale provided a corrosion rate of 12.91 µm·year-1, which is in the same order that that obtained at lab-scale. The differences between lab and plant results are related to the more realistic conditions found in plant, since measurements were taken after 7000 h of operation. Results showed the strong potential of the developed corrosion monitoring system for assessing corrosion rates and corrosion mechanisms in parabolic-trough concentrated solar power plants.