The effects of cold rolling and heat treatment on enhancing molten nitrate corrosion resistance of High-Al 310S stainless steel

Solar thermal power generation technology offers a promising solution for providing long-term, stable, and cost-effective electricity. However, severe corrosion caused by material contact with nitrates remains a major challenge that limits their extended use in high-temperature environments. 310S stainless steel is among the candidate materials considered for the construction of molten salt storage tanks. To enhance its corrosion resistance in nitrate-based environments, this study developed a 310S alloy containing 3 wt.% Al and subjected it to cold rolling followed by both solution treatment and annealing. The corrosion behavior of the treated samples was evaluated at 600 °C in a binary nitrate molten salt mixture (NaNO 3 /KNO 3 = 60/40 wt.%). Results indicate that the High-Al 310S thin plates exhibit significantly improved corrosion resistance under these conditions. Compared to the annealed samples, the solution-treated samples showed lower corrosion rates, with the minimum rate reaching 52.61 μm/year. The outer layer of the corrosion products mainly consisted of NaFeO 2 , and a protective composite oxide film composed of Al 2 O 3 , Cr 2 O 3 , and NiO formed on the surface. This compact oxide film effectively hindered the penetration of corrosive species from the molten salt into the substrate and reduced the outward diffusion of metallic elements, thereby enhancing overall corrosion resistance. These findings offer essential theoretical foundations and technical guidance for the design and selection of structural materials and processing techniques used in high-temperature molten salt applications.