Corrosion behavior of different alloys in novel chloride molten salts for concentrating solar power plants

Abstract

The molten salt thermal energy storage system is the most important composition of concentrating solar power plants, resulting in the corrosion behavior of alloys in molten salts is essential to be analyzed to ensure the long-term stability of the system. In this study, the corrosion behavior of TP347H stainless steel, Haynes230 and Inconel625 alloys was investigated in a self-developed novel molten chloride salt (24.5 wt% NaCl-8.2 wt% KCl-67.3 wt% CaCl₂). The corrosion mechanism of the alloy samples in molten chloride salts was analyzed through the microscopic characterization and elemental analysis tests. The evolution of alloy sample mass loss versus corrosion time and the main influential factors of the corrosion were analyzed. Corrosion pits appear on the surface of the alloy samples with the increasing corrosion time. Distinct corrosion cracks is observed that on the surface of the Inconel625 sample. Under the condition of 600 °C, the average corrosion rate of TP347H stainless steels is2383.628 μm·a⁻¹, and those of Haynes230 and Inconel625 are 487.639 μm·a⁻¹ and 5437.520 μm·a⁻¹. The protective oxide layer within TP347H stainless steels corrosion layer effectively inhibited further matrix corrosion. The superior corrosion resistance of Haynes230 can be attributed to its higher Ni and W content. These results are significant for optimizing the usage of novel molten salts and alloys to achieve long-term stability of the concentrating solar power plants.