Understanding the Anti-Corrosion Mechanism of Graphene Based Composite Coatings

Abstract

The aim of this thesis was to study the performance of graphene based composite coatings, as a means to replace commercially used chromate coatings and to elucidate the mechanism by which they provide protection. The results are separated into two sections, with the first section focusing on the characterisation of relevant graphene and reduced graphene oxide (rGO) flakes, and the second evaluating the performance of various graphene based composite coatings. Characterisation focused on understanding the properties of two different graphene flakes (supplied from Talga Resources Ltd and Thomas Swan, respectively) and an rGO flake form Abalonyx. Analysis showed that despite all the samples having similar lateral flake dimensions, the number of stacked layers varied. Moreover, the Thomas Swan graphene sample was defect free, whereas the Talga graphene possessed a large concentration of defects. Initial work regarding the performance of the graphene coatings focused on replicating previous published work, which found that graphene enhanced the protective nature of silane coatings. However, although the same formulation was replicated in this thesis, it was not possible to duplicate the performance. This failure is primarily attributed to holidays in the coating film, but it is also believed that the large concentration of defects in the Talga graphene may have also contributed to the poor performance. Therefore, alternative silane and epoxy formulations were investigated incorporating the more pristine Thomas Swan graphene. The silane formulation used the graphene dispersed in water, which was shown to be an unstable system that did not form an even coverage on the surface. Instead, the graphene agglomerated rapidly and failed to provide the underlying steel substrate with protection. Finally, the pristine graphene or rGO were added to an epoxy formulation, with both enhancing the barrier properties of the coating. A particular highlight, is that the graphene protected the sample at scratched sites, with graphene detected in these exposed areas, suggesting the possibility that graphene may have active corrosion protection properties.

Date of Award	1 Aug 2020
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Michele Curioni (Supervisor) & Rob Lindsay (Supervisor)