Effects of oxygen concentration on the passivation of Si-containing steel during high-temperature oxidation

The relationship between the passivation period of Si-containing steel and oxygen concentrations was investigated by conducting the oxidizing experiments employing four different oxygen concentrations on a simultaneous thermal analyzer (STA) at a heating temperature of 1260°C. The results show that the duration of passivation period increased with the increasing oxygen concentration. Moreover, the passivation period occurred at the oxygen concentrations ranging from 2.0 vol.% to 3.0 vol.%, whereas no visible passivation period was observed at the oxygen concentrations ≤1.5 vol.%. In addition, the oxidation mass gain versus time followed a linear relationship before the passivation period, which lasted for about 20 min when the mixed binary atmosphere was introduced into the sample chamber right from the beginning of the heating process.