A Synchrotron‐Based Study of the Mary Rose Iron Cannonballs. Issue 25 (8th March 2018)

• Record Type: Journal Article
• Authors: Simon, Hayley; Cibin, Giannantonio; Robbins, Phil; Day, Sarah; Tang, Chiu; Freestone, Ian; Schofield, Eleanor
• Is Part Of: Angewandte Chemie international edition. Volume 57:Issue 25(2018)
• Page Start: 7390
• Page End: 7395
• Publication Date: 2018-03-08
• Subjects: archaeology -- chlorine -- corrosion -- iron -- X-ray absorption spectroscopy; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201713120
• Languages: English
• ISSNs: 1433-7851

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 (Na2 CO3 /NaHCO3 ); however, hibbingite, β‐Fe2 (OH)3 Cl, 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)3 Cl at near‐neutral pH. Abstract : After excavation, iron artefacts are at risk of loss or damage from corrosion, which may be accelerated by the presence of Cl − . This has led to the development of conservation treatments to remove chlorine. Thirty years of conservation applied to cannonballs from the Mary Rose shipwreck are reviewed, using synchrotron‐based techniques to assess the impact of conservation choices on iron corrosion.