[Back]

C. Merola, H. Cheng, D. Dworschak, C. Ku Chiang, F. Renner, M. Valtiner:
"Nanometer Resolved Real Time Visualization of Acidification and Material Breakdown in Confinement";
Advanced Materials Interfaces, 6 (2019), 10; 180206901 - 180206911.

Localized surface reactions in confinement are inherently difficult to visualize
in real-time. Herein multiple-beam-interferometry (MBI) is extended as a
real-time monitoring tool for corrosion of nanometer confined bulk metallic
surfaces. The capabilities of MBI are demonstrated, and the initial crevice
corrosion mechanism on confined nickel and a Ni75Cr16Fe9 model material
is compared. The initiation of crevice corrosion is visualized in real time
during linear sweep polarization in a 1 × 10−3 m NaCl solution. Pre- and
post-experiment analysis is performed to complementarily characterize the
degraded area with atomic force microscopy (AFM), optical microscopy,
nano-Laue diffraction (nano-LD), scanning electron microscopy (SEM)/
electron backscatter diffraction (EBSD), and X-ray photoelectron spectroscopy
(XPS). Overall, Ni75Cr16Fe9 displays a better corrosion resistance; however,
MBI imaging reveals 200 nm deep severe localized corrosion of the alloy
in the crevice opening. Chromium rich passive films formed on the alloy
contribute to accelerated corrosion of the confined alloy by a strongly
acidifying dissolution of the passive film in the crevice opening. Nano-LD
further reveals preferential crystallographic defect and corrosion migration
planes during corrosion. MBI provides nanometer accurate characterization
of topologies and degradation in confined spaces. The technique enables
the understanding of the initial crevice corrosion mechanism and testing
modeling approaches and machine-learning algorithms.

http://dx.doi.org/10.1002/admi.201802069