Corrosion Behaviour of 316 Stainless Steel in Molten CaCl2-CaF2-CaO Salts at High Temperature
DOI:
https://doi.org/10.24425/afe.2025.155348Abstract
One of the major limitations of using molten salts for CO2 capture processes from industrial gas streams is the availability of construction materials with adequate corrosion resistance. This is due to the high operating temperature of the process and the aggressive environment of chloride-fluoride molten salts. In this study, the influence of temperature and a molten, eutectic mixture of CaCl2 - CaF2 with the addition of 10 wt.% CaO on the behavior of SS316 steel was evaluated. Tests were conducted at 700 °C and 950 °C for 40, 80, and 120 hours. Material samples were weighed before and after the tests, and selected samples underwent microscopic analysis (SEM, EDS), measurements of the corrosion product layer thickness, and wall thickness. The corrosion rate of SS316 steel was also determined. The results showed, among other findings, that at 700 °C, mass losses were minimal (max. 0.5%), and the corrosion layer had an average thickness not exceeding 8.2 μm. At 950 °C, mass loss increased to 3.85%, and the corrosion product layer reached an average thickness of 83 μm. Intergranular corrosion was also observed, along with enrichment of the corrosion layer with salt elements (Ca, O, Cl) and steel alloying elements (Cr, Ni). Additionally, segregation of Cr, Mn, and Mo was noted at grain boundaries. The calculated corrosion rate of SS316 steel at 700 °C was 171 μm/year, while at 950 °C, it was significantly higher at 1540 μm/year.References
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