Corrosion behavior and mechanism of UNS N10003 alloy in NaCl-KCl-CaCl2 molten salt and vapor at 800 °C

• Corrosion of UNS N10003 in NaCl-KCl-CaCl 2 molten salt and vapor was first studied. • HCl gas is detected in the NaCl-KCl-CaCl 2 molten salt at 800 °C. • First-principles calculation was used to study the existing states of O in the alloy. • O will preferentially react with Cr to form chromium oxides in the grain boundaries. Corrosion of UNS N10003 alloy in NaCl-KCl-CaCl 2 molten salt and vapor was investigated at 800 °C for 500 h. Corrosion depth of UNS N10003 alloy in NaCl-KCl-CaCl 2 salt and vapor reaches up to 104.3 and 35.0 μm, respectively. UNS N10003 alloy suffered severe intergranular and pitting corrosion. Cr, Fe, Ni and Mo were obviously depleted. Chromium oxides were formed inside the intergranular and alloy surface after corrosion. Existing states of O in alloy were further explored through theoretical calculations, indicating that O preferentially reacts with Cr to form chromium oxides in grain boundaries.