Synergistic effect of Cl- and F- on the corrosion behavior and mechanism of 316 stainless steel in NaNO3-based molten salts and vapor

The corrosion behaviors of 316 stainless steel (316 SS) in NaNO3-NaCl-NaF molten salt and vapor were investigated at 450 degrees C for 130 h under argon gas and air conditions, respectively. 316 SS suffered from weight gain under the argon gas condition yet experienced weight loss under the air condition. Fe-O enriched layer with different crystal forms (i.e., whisker-like, flake, and grain shapes) was detected by XRD. The crystal forms were relatively homogeneously distributed after the NaNO3-NaCl-NaF molten salt corrosion but were not uniform after the NaNO3-NaCl-NaF vapor corrosion. 316 SS experienced a more serious corrosion attack in salts vapor than that in NaNO3-NaCl-NaF molten salt regardless of the experimental condition. The corresponding corrosion mechanisms were also investigated, and results show that the oxides helped mitigate further corrosion attacks. These findings provide direct guidelines for choosing the appropriate molten salts and alloys for CSP.

Automated summary

The corrosion behaviors of 316 stainless steel in NaNO3-NaCl-NaF molten salt and vapor were investigated at 450°C. The results showed that weight gain occurred in argon gas condition while weight loss occurred in air condition. Fe-O enriched layer with different crystal forms was detected by XRD. The crystal forms were relatively homogeneously distributed after molten salt corrosion but not uniform after vapor corrosion. 316 stainless steel experienced a more serious corrosion attack in salts vapor than in molten salt.