Impact of temperature on corrosion behavior of austenitic stainless steels in solar salt for CSP application: An electrochemical study

The compatibility between solar salt and structure materials is still a key issue in concentrated solar power (CSP) technology. The corrosivity of solar salt is significantly dependent on temperature. In this work, the temperature effect on the corrosion of 304 and 316L stainless steels (SS) in solar salt was studied at 500, 565, and 600 °C using electrochemical methods. Results indicate that higher values of i_corr and corrosion rate (CR) are found for both 304 and 316L SS at higher temperatures. EIS results demonstrate that corrosion process of 304 SS in solar salt at 500 and 565 °C is controlled by ions transportation through the oxide layer. At 600 °C, however, the Warburg impedance is observed due to the porous and Cr₂O₃-free oxide layers formed on the surface of the sample exposed in molten solar salt for 138 h. Comparatively, the ions transportation through the oxide layer is always the rate-controlling process for 316L SS at each temperature. Protective oxide layer containing Cr₂O₃ is formed on 316L SS even at 600 °C. Moreover, the formation of Cr-rich nitride underneath the oxide/substrate interface depends on the temperature of melt and chemical composition of substrate.