Influence of gaseous atmosphere on electrochemical behavior of nickel alloys in LiCl-KCl-Na2SO4 at 700 °C

Electrochemical behavior of Ni alloys (Ni, β-NiAl, β-NiAl/Cr) was investigated in LiCl-KCl-Na2SO4 electrolyte at 700 °C under three gaseous atmospheres (Ar, O2, O2-0.1%SO2). In oxidizing atmospheres, Ni rapidly degraded due to instability of NiO, and alumina-rich scale on β-NiAl provided limited protection against hot corrosion (e.g., cracks in the scale under O2-0.1%SO2); however, the addition of both Al and Cr resulted in enhanced corrosion resistance by forming a mixed-oxide (Al2O3-Cr2O3) scale in oxidizing atmospheres. In hot corrosion processes of Ni alloys, the formation and stability of oxide scales in the molten salt were influenced by gaseous atmosphere and alloying elements.