a Ion-polishing process used to prepare samples for cross-sectional SEM imaging. b Schematic of the irradiated (in orange) and unirradiated (in green) zones for interpreting zones of SEM images. c–h Representative SEM images from different zones of Ni-20Cr samples under different beam current densities. Scale bar: 20 μm. c–e Show the irradiated zone, with white dashed-lines indicating the deepest attack. f–h Show the unirradiated zone. i Data analysis process for the Ni-20Cr foils. j Cumulative distribution function (CDF) of normalized corrosion depth, which is defined as corrosion depth normalized by sample thickness using data obtained by process in i. Dash lines represent data from the corrosion/irradiation region. Solid lines represent data from the corrosion only region. Blue, yellow, and dark green represent beam current densities of 1.5, 2.0, and 2.5 μA cm−2, respectively. k Average, normalized corrosion depth using data from the 10% deepest corroded regions of each sample, as illustrated by the light red bar in j. Diagonal-filled bars represent data from corrosion/irradiation region. Solid bars represent data from corrosion only region. Meaning of colors is the same with j. Error bars denote one standard deviation.