| Popis: |
Pure iron has been oxidized, at atmospheric pressure, in a range of COCO2 mixtures at 500°C, and in 1·5%COCO2 over the temperature range 350–600°C. Weight gains, measured in situ on an electronic microbalance, fitted a parabolic law for the duration of the experiments (∼ 150 h) under all conditions, except when the proportion of CO exceeded 30%. The parabolic rate constant can be expressed as k=1⋅47×105(PcoPco2)−0.29exp(−30,000RT)g2m−4s−1 . At higher levels of CO (⩾ 40%) significant carbon deposition occurs. It is shown that in 40%CO this causes a change in the oxidation kinetics from parabolic to linear. It is suggested that the breakaway corrosion of mild steel in CO2 at high pressure can be accounted for by the concentration of CO within a porous oxide. |
