Advanced STEM/EDX investigation on an oxide scale thermally grown on a high-chromium iron–nickel alloy under very low oxygen partial pressure

•A scale grown on a high-chromium iron–nickel alloy under low oxygen partial pressure was studied.•STEM-EDX maps at high resolution on a transversal thin lamella have been conducted.•The real complexity of the oxide layer has been highlighted.•These results explain the elevated number of semiconducting contributions.

A thermal oxide scale has been grown on a high-chromium iron-nickel alloy under very low oxygen partial pressure (1050 °C, 10−10 Pa). In this paper, a special attention has been paid to morphological and chemical characterizations of the scale by scanning transmission electron microscopy and energy dispersive X-ray analysis at high resolution on a cross-section thin lamella beforehand prepared by using a combined focused ion beam/scanning electron microscope instrument. The complexity of the oxide layer is highlighted, and the correlation between the present results and the ones of a photoelectrochemical study is discussed.