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Instruments / Technical Area	Publication Details	Published
B18-Core EXAFS I11-High Resolution Powder Diffraction	Fe K-edge X-ray Absorption Spectroscopy of corrosion phases of archaeological iron: results, limitations, and the need for complementary techniques Hayley Simon , Giannantonio Cibin , Ian Freestone , Eleanor Schofield Journal Of Physics: Condensed Matter DOI: 10.1088/1361-648X/ac08b6 Diamond Proposal Number(s): [16328] Open Access Show Abstract ▼ Abstract: Data analysis methods for iron X-ray Absorption Spectroscopy (XAS) can provide extensive information about the oxidation state and co-ordination of an Fe-species. However, the extent to which techniques developed using a single-phase iron sample may be applied to complex, mixed-phase samples formed under real-world conditions is not clear. This work uses a combination of pre-edge fitting and linear combination analysis (LCA) to characterise the near edge region of the X-ray absorption spectrum (XANES) for a set of archaeological iron corrosion samples from a collection of cast iron cannon shot excavated from the Mary Rose shipwreck and compares the data with phase compositions determined by Synchrotron X-ray Powder Diffraction (SXPD). Archaeological powder and cross-section samples were compared to a library of iron standards and diffraction data. The XANES are consistent with previous observations that generation of the chlorinated phase akaganeite, β-FeO(OH,Cl), occurs in those samples which have been removed form passive storage and subjected to active conservation. However, the results show that if any metallic species is present in the sample, the contribution from Fe(0) to the spectral region containing a pre-edge for oxidised iron – Fe(II) and Fe(III) – causes the analysis to be less effective and the conclusions unreliable. Consequently, while the pre-edge fitting methodology may be applied to a mixture of iron oxides or oxyhydroxides, the procedure is inappropriate for a mixed metal-oxide sample without the application of a complimentary technique, such as SXPD.	Jun 2021
B18-Core EXAFS I11-High Resolution Powder Diffraction I12-JEEP: Joint Engineering, Environmental and Processing	Influence of microstructure on the corrosion of archaeological iron observed using 3D synchrotron micro-tomography H. J. Simon , G. Cibin , C. Reinhard , Y. Liu , E. Schofield , I. C. Freestone Corrosion Science DOI: 10.1016/j.corsci.2019.108132 Diamond Proposal Number(s): [16863, 16328] Show Abstract ▼ Abstract: A combination of X-ray analytical techniques has been used to study the microstructure and corrosion of a 450-year-old cast-iron cannonball fragment from the Mary Rose shipwreck. Using a 3D approach, it has been shown that akaganeite, β-FeO(OH, Cl), starts to appear ˜1.5 mm below the outer surface of the object, occurring selectively around non-contiguous graphite flakes in the microstructure, with no corrosion in graphite-free regions. This spatial analysis has given a new look inside a 450-year-old system, to see how metallographic features interact with local chemical environments to give complex corrosion products, centuries in the making.	Aug 2019
B18-Core EXAFS I11-High Resolution Powder Diffraction	A Synchrotron-based study of the Mary Rose iron cannonballs Hayley Simon , Giannantonio Cibin , Phil Robbins , Sarah Day , Chiu Tang , Ian Freestone , Eleanor Schofield Angewandte Chemie International Edition 30 DOI: 10.1002/anie.201713120 Diamond Proposal Number(s): [16328] Open Access Show Abstract ▼ Abstract: Post-excavation iron corrosion may be accelerated by the presence of Cl−, leading to conservation methods designed to remove Cl. This study exploits a unique opportunity to assess 35 years of conservation applied to cast-iron cannon shot excavated from the Mary Rose. A combination of synchrotron X-ray powder diffraction (SXPD), absorption spectroscopy (XAS), and fluorescence (XRF) mapping have been used to characterise the impact of conservation on the crystalline corrosion products, chlorine distribution, and speciation. The chlorinated phase akaganeite, β-FeO(OH,Cl), was found on shot washed in corrosion inhibitor Hostacor IT with or without an additional reduction stage. No chlorinated phases were observed on the surface of shot stored in sodium sesquicarbonate (Na2CO3/NaHCO3); however, hibbingite, β-Fe2(OH)3Cl, was present in metal pores. It is proposed that surface β-FeO(OH,Cl) formed in the early stages of active conservation owing to oxidation of β-Fe2(OH)3Cl at near-neutral pH.	Mar 2018

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