Enhanced High-Temperature Corrosion Resistance of AISI 301LN Stainless Steel in Silica-Doped Ternary Carbonate Nanofluids for Thermal Energy Storage Applications

Molten carbonate salt nanofluids have emerged as a promising approach to improve the power generation efficiency of next-generation concentrated solar power (CSP) systems due to their enhanced thermophysical properties at high temperatures. However, corrosion upon salt nanofluids remains a key challenge for the use of cost-effective steels as construction materials in CSP applications. In this work, the corrosion behavior of AISI 301LN stainless steel exposed to molten carbonate salt nanofluids containing 1.0 wt.% SiO2 nanoparticles with <20 nm and <50 nm has been studied. Corrosion tests were conducted in a static Li2CO3-Na2CO3-K2CO3 molten salt mixture at 600 °C for 1000 h. The oxide scales formed after exposure to the three nanofluids and the base salt were compared. The results revealed that the corrosion rate of AISI 301LN steel on molten salt was reduced by the addition of SiO2 nanoparticles. The incorporation of SiO2 nanoparticles into the oxide scale leads to the formation of dense reticulated nanostructures composed of Si-containing oxides, respectively. This increases the hardness of the oxide scale and enhances its protective performance in molten salt, particularly when using SiO2 nanoparticles with the smallest size (<20 nm).