Executive Summary : | High temperature corrosion of thermal energy storage (TES) materials (used for containing/storing molten salt which acts as a thermal energy storage media) by molten chloride salts is one of the major issues in the concentrated solar power (CSP) plants. In this regard, several preventive techniques like inhibitors, coating, and regular salt purification have been adopted in order to minimize the corrosion rate of the TES materials. However, these preventive techniques are only system specific and not effective to the expected extent. Further, to compete with the conventional thermal power plant, it is necessary to increase the proficiency of thermal to electrical energy conversion in CSP plants by increasing operating temperature. Towards this, future generation CSP plants demand high corrosion resistant TES materials for better performance. Therefore, the proposed work is aimed to develop microstructurally engineered high corrosion resistant TES materials through optimization of microstructural parameters (i.e., grain size and distribution, residual strain, texture, grain boundary character and connectivity), so that it can withstand the aggressive environments for longer duration. Furthermore, even though the addition of inhibitors to molten chloride salts has been considered as a feasible method to minimize the corrosion rate of the materials, this technique is presently not available at an industrially viable state due to lack of understanding of the exact role (principles/mechanisms) of inhibitors in molten salts. Therefore, the second objective of the proposed work is to develop and optimize the suitable inhibitors to suppress the corrosion rate of the TES materials in the presence of molten salts. In this proposed work, an in-house developed high temperature electrochemical corrosion cell (Hi-TEC) setup would be employed to execute the aforementioned two objectives through various electrochemical techniques such as open circuit potential, potentiodynamic polarization, potentiostatic polarization, impedance spectroscopy analysis. Eventually, the proposed study would lead to a better understanding of the effect of various microstructural features and inhibitors on molten chloride salt corrosion behaviour of TES materials. Further, the present work would also provide a roadmap to enhance the high temperature corrosion resistance of the TES materials through microstructural engineering and/or doping inhibitors in molten salts. Such high corrosion resistant TES systems are expected to withstand against molten salt corrosion in the next generation CSP plants which would ultimately improve the efficiency of the energy production and hence cost saving. |