Reaction Mechanism of Preoxidized Nickel-Chromium-Cerium Alloy with Chlorine Gas in the Temperature Range 400°C to 700°C

Abstract

Abstract High-temperature corrosion of preoxidized Ni-Cr-Ce alloys in chlorine gas (Cl2 ) at temperatures between 400°C and 700°C was investigated using thermogravimetric analysis and examining the corrosion 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 role in the chlorination processes. With increasing reaction temperatures, the oxide scale was destroyed after exposure to Cl2 for a period of time. The corrosion rate increased rapidly, and weight descreased linearly with time. In Cl2 atmospheres at high temperature, Cl2 attacked the oxide scale by three mechanisms: mechanical damage by volatile chlorides, scale pitting and spalling by Cl2 dissolving in the scale, and oxides being converted to chlorides.