Kinetics of metal dusting corrosion of of Fe-Ni-Cr(-Al) alloys

There is a pursuit for maximum efficiency in steam-reforming technologies in the petrochemical industry and a rising interest in the Fischer-Tropsch gas-to-liquid (GTL) hydrocarbon processing technologies. These require higher carbon content and lower water vapour content in the syngas (CO/H2-based gas atmospheres). Fe-based (steel) and Ni-based high chromium alloys are widely applied as high temperature materials in the petrochemical industry. In the temperature range 450-850 °C all Fe-based and Ni-based metals in high temperature process equipment that get into contact with carbon-bearing gases, like syngas, are subjected to carburization, i.e. dissolution of carbon in the alloy and the development of carbides. Generally, in the petrochemical industry and, particularly, in the reforming units, such carburization may lead to a very aggressive corrosion phenomenon known as metal dusting (MD), also called catastrophic carburizing. During MD the protective chromium (and aluminum) oxide layer on the Fe-based and Ni-based alloys is attacked locally. The stochastic nature of MD has hitherto hindered a thorough investigation of the parameters influencing the kinetics of the (catastrophic) carburizing process and, thus, targeted optimization of the alloys’ compositions.