Oxide scale formations in CH4-H2O atmospheres were compared for different alloys as interconnects in solid oxide fuel cells (Fe-Cr and Ni-Cr alloys). Oxidation with anode gases (CH4, H2O, CO, and CO2) caused a relatively thick oxide scale formation on the alloy surfaces even in the low oxygen partial pressures at 1073 K. The distribution of elements in the oxide scale and the growth rates of oxide scales were precisely analyzed among the examined alloys by glow discharge optical emission spectrometry. Mn spinels formed on the top surface of oxide scales for both Fe-Cr and Ni-Cr alloys. Oxide scale thickness grew with annealing time by a parabolic relationship, and the growth rates were in the orders of 10(-6)-10(-5) mu m(2) s(-1) at 1073 K. Ni-Cr alloy shows relatively low growth rate compared with the Fe-Cr alloy. The electrical conductivity after forming oxide scales was different depending on the oxide scale phases and thickness, which was on the order of 10-100 S cm(-1) at 1073 K. (c) 2005 The Electrochemical Society.