# Synchrotron x-ray studies of atmospheric pitting corrosion of stainless steel

Mi, Na (2014). Synchrotron x-ray studies of atmospheric pitting corrosion of stainless steel. University of Birmingham. Ph.D.

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## Abstract

Atmospheric pitting corrosion of stainless steel was studied to determine pit growth mechanisms and kinetics. Inkjet printing of chloride was used to investigate the growth of atmospheric corrosion pits. It has been shown that the pit size increases with increasing chloride deposition density, as well as increases with increasing deposit diameter. Atmospheric pit growth was characterised in situ and in real time with synchrotron X-ray microtomography. Most pits were found to have open mouths and shallow depths. Growth of a deep pit was also observed in a pre-existing defect. Pit growth in depth does not appear to be under diffusion control. Electrochemical kinetics of the metal dissolution reaction including the Tafel slope as well as the critical metal ion concentration for pit propagation were studied with lD artificial pits in high chloride concentration solutions relevant to atmospheric conditions. The diffusion-limited current density and ratio of the critical metal ion concentration for pit propagation to the saturation concentration were found to decrease with increasing chloride concentration. However, there is no significant effect of the chloride concentration on the Tafel slope. The pitting potential and repassivation potential were measured on abraded wires and were found to decrease with increasing chloride concentration. Salt layer formation has been observed on ID artificial pits in 1 M and 6 M solutions with synchrotron XRD. The dominant phase of the salt layer was found to be FeCl$$_2$$•4H$$_2$$0. The formation of FeCl$$_2$$•2H$$_2$$0 was also observed, predominantly at higher applied potentials. This work can be used to provide a basis for developing a model to predict pitting corrosion of stainless steel under atmospheric corrosion conditions, for example in the case of storage of stainless steel intermediate nuclear waste containers.

Type of Work: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
Supervisor(s):
Supervisor(s)EmailORCID
Davenport, AlisonUNSPECIFIEDUNSPECIFIED
Rayment, TrevorUNSPECIFIEDUNSPECIFIED
Licence:
College/Faculty: Colleges (2008 onwards) > College of Engineering & Physical Sciences
School or Department: School of Metallurgy and Materials
Funders: None/not applicable
Subjects: T Technology > T Technology (General)
T Technology > TN Mining engineering. Metallurgy
URI: http://etheses.bham.ac.uk/id/eprint/4558

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