The feedback mode of a scanning electrochemical microscope (SECM) was applied to study differences in the reactivity of a highly alloyed austenitic stainless steel. Alloy 926 (UNS N08926), in its unsensitised and sensitised state. Alloy 926 was heated at 825 degrees C for 1 h in an inert atmosphere in order to produce a sensitised metallurgical condition. Sensitisation was due to chromium carbide formation at the grain boundaries. The oxygen reduction reaction was used as an indicator to monitor the effect of the sensitisation process on the corrosion activity of the Alloy 926 surface in a 35 gl(-1) NaCl solution. Higher oxygen consumption was observed above the sensitised sample than above the unsensitised sample due to differences in the oxide films of the two alloy conditions. (C) 2012 Elsevier Ltd. All rights reserved.