Comprehensive Near Edge X-ray Absorption Fine Structure analysis of corrosion in Iron at the nanoscale

Abstract

Corrosion continues to be a major global challenge representing 3% of the GDP of industrialized nations. However, there are still many unanswered scientific and technical questions about the corrosion process and the corrosion products that iron forms. It is not clear which of the many iron oxides, hydroxide and oxyhydroxides form as a scale, particularly under the many different environmental conditions that corrosion can occur under. This is partly due to, for example, similarities in the crystal structures, such that even diffraction cannot resolve them all easily. In this work, we illustrate the use of Near Edge X-ray Absorption Fine Structure in conjunction with high resolution Scanning Transmission X-ray Microscopy to characterize iron corrosion scales at the nanoscale and identify the formation of several coexisting iron phases. Importantly, these phases include magnetite, a ferrimagnetic material. Hence, we briefly consider the use of X-ray magnetic circular dichroism to provide additional magnetic contrast as a further means of resolving the possible iron phases and possible enhancements for subsequent experiments.