REACTION-MECHANISM OF PREOXIDIZED NICKEL-CHROMIUM-CERIUM ALLOY WITH CHLORINE GAS IN THE TEMPERATURE-RANGE 400-DEGREES-C TO 700-DEGREES-C

High-temperature corrosion of preoxidized Ni-Cr-Ce alloys in chlorine gas (Cl-2) at temperatures between 400 degrees C and 700 degrees C was investigated using thermogravimetric analysis and examining the corro sion products by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Corrosion resistance of preoxidized alloys against chlorination was improved by formation of protective nickel oxide-chromium oxide-cerium oxide (NiO-Cr2O3-CeO2 ) scale. At lower temperature, the protective oxide Scale played a rol e in the chlorination processes. With increasing reaction temperatures , the oxide scale was destroyed after exposure to Cl-2 for a period of time. The corrosion rate increased rapidly, and weight descreased lin early with time. IR Cl-2 atmospheres at high temperature, Cl-2 attacke d the oxide scale by three mechanisms: mechanical damage by volatile c hlorides, scale pitting and spalling by Cl-2 dissolving in the scale, and oxides being converted to chlorides.