High resolution electrochemical measurements for corrosion

Abstract

Scanning electrochemical cell microscopy (SECCM) is a recently developed technique that has the ability to perform multiple reproducible electrochemical measurements with very high spatial resolution at surfaces. Despite its success in the study of nanoparticle electrocatalysis and carbon nanomaterials, SECCM has yet to be applied to the field of corrosion science. This thesis presents the first efforts to utilise SECCM as a tool to study corrosion related phenomena. In this work, comparisons are made between SECCM and similar techniques that are currently used in corrosion science to identify where SECCM can be most effective and how it can improve on these existing methods. The corrosion related behaviour associated with the microstructural features of metals and alloys (e.g. grain orientation, grain boundaries, and inclusions) is a popular topic amongst researchers adopting high resolution electrochemical methods. Considering the recent success of applying SECCM to resolve the relationship between electrochemical behaviour and surface structure, this proved to be the ideal topic to introduce SECCM into corrosion science. The relationship between the crystal orientation of grains on polycrystalline metals and the rates of various corrosion related processes, including: anodic dissolution, cathodic hydrogen evolution, passive behaviour, and hydrogen absorption, in neutral and acidic media is revealed successfully in this work. The electrochemical behaviour of individual nanoscale inclusions and grain boundaries is also investigated. These results were collected using SECCM in combination with various complementary and correlative surface characterisation techniques (e.g. electron backscatter diffraction, and energy dispersive spectroscopy) applied to the same electrode region as the SECCM measurements, and computational methods (e.g. density functional theory). In summary, this thesis has shown that SECCM has the ability to contribute significantly in the field of corrosion science