Oxidation mechanism of Fe–16Cr alloy as SOFC interconnect in dry/wet air

•A special thermodynamic description corresponding to the kinetics was applied.•We reported the relationships of degradation time with temperature and moisture.•”Turning time” in the Fe–16Cr alloy oxidation kinetic model was given.•The oxidation mechanism of Fe–16Cr alloy in the wet air was discussed.

Experimental study on the oxidation corrosions of Fe–16Cr alloy was carried out at 800–1100 °C under dry/wet air conditions. Faster oxidation rate was observed at higher temperature and water vapor content. The degradation time td between two stages in oxidation process showed an exponential relationship with elevating corrosion temperature in dry air, and a linear relationship with the water content in the case of water vapor introduced to the system.The mechanism of oxidation corrosions of Fe–16Cr alloy was suggested by the Real Physical Picture (RPP) model. It was found that the break-away oxidation in stage II was controlled by diffusion at initial both in dry and wet air, then became linear with the exposure time, which implied that the oxidation rate was then controlled by chemical reaction of the interface between the metal and the oxidized scale. Moreover, the effect of water in the oxidation process is not only to supply more oxygen into system, but also to modify the structures of oxide scale due to the existence of hydrogen atom, which results in the accelerated corrosions.