Morphology of oxide scale formed on Fe-20Cr-4Al alloys with small amounts of sulfur contained was studied up to 5 cycles (1 cycle=18.0ks) at 1373-1673K in oxygen of 101kPa. Morphology of oxide scale on Fe-20Cr-4Al-3ppm S alloy was planar after any tempreture of oxidation. On the other hand, that of oxide scale on Fe-20Cr-4Al-(35, 53, 104 and 171ppm) S alloys showed a tendency to planar from convolted with increasing sulfur contents after 5 cycles at 1373K.
