Fig. 2 | npj Materials Degradation

Fig. 2

From: Localized corrosion of low-carbon steel at the nanoscale

Fig. 2

Aqueous corrosion of 1018 steel visualized by in-situ STEM. Scale bar indicates 200 nm. The PED crystallographic orientation map and bright-field STEM micrographs depict the region where localized corrosion was observed. Liquid exposure times are provided in each panel. Regions of increasing intensity resulted from increased transmission of the beam (cf) and correspond to localized corrosion events. Grain boundaries are delineated in yellow to facilitate comparison between panels, and insets show a schematic of the grain boundaries with regions experiencing localized corrosion highlighted in pink. a PED map indicating the various crystallographic orientations in the body-centered cubic (α-ferrite) reference plane. Black pixels denote non-BCC phases (i.e., cementite). b BF-STEM micrograph showing the microstructure of this region in vacuum prior to exposure to the aqueous electrolyte; the cementite grain inclusion was completely bordered by a ferrite matrix. TJ1, TJ2, and TJ3 are indicated with white arrows. cf BF-STEM micrographs depicting this region during exposure to flowing aqueous solution. c Localized corrosion at the inclusion was first observed at the triple junction (white arrow) between Fe3C, αA, and αB (TJ1). Total electron flux 0.905 e2*s. d At 45 min, localized corrosion was observed to have claimed the interface between the Fe3C grain and grains αA/αB/αC, as well as the triple junctions (white arrows) formed by Fe3C/αB/αC (TJ2) and Fe3C/αE/αF (TJ3). Total electron flux 0.915 e2*s. e At 47 min, the localized corrosion area stopped evolving. Total electron flux 1.23 e2*s. f Final in-situ micrograph acquired after 102 min of solution exposure. Total electron flux 5.15 e2*s

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