Corrosion behavior of iron-based and Ni-based alloys melted in NaCl–MgCl2–KCl mixed molten salt under vacuum atmosphere

Abstract

In this work, static immersion and gravimetric methods were used to study the corrosion behavior of three common stainless steels and four Ni-based alloys in a NaCl–MgCl2–KCl mixed molten salt under vacuum atmosphere. The corrosion test was conducted at 700 °C, with a maximum exposure time of 100 h. Corrosion behavior was determined by measuring the mass loss of the sample at different time intervals and the corrosion rates at 100 h. The microstructure of the alloy was analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic force microscope (AFM), and X-ray diffraction (XRD). The results showed that stainless steels were generally more severely corroded than Ni-based alloys. 304 stainless steel and In800H exhibited the worst corrosion resistance, whereas Ni-based alloy In625 had the best corrosion resistance. Fe and Cr were dissolved in the molten chloride salts and reacted with the molten chloride salts. Mo played a positive role in suppressing the corrosion of the alloys in molten chloride salts by inhibiting the outward diffusion of the elements.

Keywords

• Stainless steel
• Ni-based alloy
• Molten chloride salt
• High-temperature corrosion