Raman Singh

Abstract:

Monolayer or a few atomic layer thick graphene coatings on metals (Figure (left)) have been shown to improve their corrosion resistance by nearly orders of magnitude (Figure (right)). Though there are very few studies reported on the topic of corrosion resistance due to graphene coating, there is still considerable variability in the degree of improvement. For example, improvement in aqueous corrosion resistance of copper due to graphene coating is reported to vary from insignificant to nearly 2 orders of magnitude, whereas the improvement for nickel can be in excess of an order of magnitude. This presentation will review the most recent (2010-14) research on graphene that has been claimed as 'the thinnest known corrosion-protecting coating', and potential application of such disruptive approach to corrosion resistance of steels. The second part of the presentation will focus on the remarkable resistance to oxidation as result of the nanocrystalline alloy structure. This will include an elaborate description of the author's own hypothesis that nanocrystalline structure can impart extraordinary oxidation resistance, and the validation of this hypothesis. A thorough surface/subsurface characterization of oxidized alloys, using secondary ion mass spectrometry has provided a sound mechanistic understanding of the remarkable improvement in oxidation as result of nanocrystalline structure. The data to be presented will include the results establishing that a Fe-Cr nanocrystalline alloy with only 10wt% Cr can provide as much oxidation resistance as a Fe-20Cr alloy, suggesting possibility of Fe-Cr alloys with the necessary corrosion resistance at much lower Cr contents. As another exciting potential application of this work, the nanocrystalline powders of Fe-Cr alloys synthesized in this study could be used for developing corrosion resistance coating having considerably low Cr contents.