High-temperature corrosion of nickel-chromium alloys in flowing chlorine-water vapor environments

Corrosion of Ni-Cr alloys in chlorine (Cl-2) gases containing 0 vol% to 5.0 vol% water (H2O) vapor between 400 degrees C and 700 degrees C was investigated using thermodynamic analysis and examination of corrosion products by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and x-ray photoelectron spectroscopy (XPS). Corrosion behavior of Ni-Cr alloys in the environments studied occurred by chlorination and oxidation simultaneously. Results indicated overall kinetics of corrosion in this temperature range were influenced by the presence of water vapor. With increasing temperature, the lower partial pressure of H2O (P-H2O) had little effect on the corrosion process. At higher P-H2O, the corrosion rate decreased because of formation of a condensed Cr2O3-rich layer on the surface of the corrosion product scale formed on the Ni-Cr alloys.