Abstract The rates of reaction of the alloy 12R72HV (essentially 65.9% Fe, 15.3% Cr and 14.8% NO with Cs 2Te under a constant O 2 potential set by a Ni/NiO couple have been measured from 898 to 983 K. An electrical resistance method was used to determine the resistivity of the steel from 292 to 983 K and these data were subsequently employed in the measurement of the diminution in thickness of steel foils caused by the corrosion process. The corrosion reaction was initially mainly linear thereby indicative of an unhindered chemical process, and with an activation energy of 161 ± 22 kJ mol −1. Subsequently the kinetics became predominantly logarithmic indicating a diffusion process with activation energy of 79 ± 10 kJ mol −1. The results are compared with those for the alloy PE16 (essentially 33.7% Fe 16.5% Cr and 43.5% Ni). The alloy PE16 is less rapidly corroded than is 12R72HV steel. With both alloys, the corrosion is initially predominantly linear indicative of unhindered chemical reactions but with different activation energies (161 versus 210 kJ mol −1 for PE16). Subsequently the kinetics differ again in that 12R72HV is corroded by a logarithmic process, whereas parabolic kinetics (activation energy 229 ± 9 kJ mol −1) dominate the corrosion of PE16. The relative inertness of PE16 compared with 12R72HV is attributed to its high Ni content (43.5%). The different diffusion kinetics may be related to a slight variation in the layering of the reaction products.