Carburization of iron by CO-based mixtures in nitrogen at 925 °C

The rates of carburization by mixtures of CO, CO2, H2 and H2O in N2 have been measured gravimetrically at 925 °. The rate equation which best describes the experimental data is based on a mechanism which involves a rapid surface dissociation of CO into carbon and oxygen atoms, and a subsequent rate determining step between this atomic oxygen and either CO or H2. The CO-H2 system carburizes much faster than CO alone, because H2 combines faster with atomic oxygen than does CO. The carburizing rate constant for CO-H2 is 44 times that for CO alone. The mechanism is confirmed by the additivity of the separate rates for the CO-H2 mixtures and for CO alone.