Iron oxidation kinetics study by using infrared spectral emissivity measurements below 570 °C

The oxidation kinetics of iron below 570 °C is investigated through the dependence of the spectral emissivity on the surface oxidation state. Using the theory of radiative effects of thin films, the oxide scale thickness is obtained as a function of time. A parabolic growth has been observed in all the cases, and applying Wagner’s theory, the oxidation parabolic rate constants have been calculated at four temperatures. The temperature dependence of these results has additionally been used to obtain the activation energy of the oxidation process in iron. The parabolic rate constants and activation energy values are in good agreement with the theoretical predictions, and this suggests that the lattice diffusion mechanisms for the high temperature magnetite growth also occur until 400 °C. The experimental results are also useful to test the applicability of emissivity measurements for in situ oxidation kinetics studies in the spectral range where the scales are optically thin.