High temperature corrosion behavior of iron aluminides containing ternary additions in H2/H2S/H2O mixed gases

The high-temperature corrosion behavior of four iron aluminides containing Fe–18Al (in at.%) and three Fe–18Al–5M alloys (where M was Cr, Mn, or Mo) was studied over the temperature range of 700–900°C in a H2/H2S/H2O atmosphere. The corrosion kinetics followed the parabolic rate law in all cases, regardless of temperature and alloy composition. The parabolic rate constants decreased with decreasing temperature, and the addition of ternary elements resulted in various decreases in the corrosion rate compared with Fe–18Al. It was found that Mo was effective to improve the corrosion resistance at T≤800°C while Cr had a better improvement at 900°C. The scales formed on all iron aluminides were strongly dependent on temperature and ternary addition.