Shining a light on marine archaeological iron: understanding the kinetics and mechanisms of degradation to inform future conservation strategies

The conservation of large scale heritage structures, such as buildings and ships present particular challenges for conservation scientists. The scale and complexity of materials, their unique histories, and the difficulties of studying the systems means that the underlying mechanisms of ongoing degradation are poorly understood - which in turn results in non-optimum conservation choices. The conservation of archaeological iron from marine environments is complicated by the ingress of Cl ions whilst in the burial environment from seawater. Despite extensive washing, residual Cl typically remains bound in these structures and this can rapidly react with iron on drying to form expansive corrosion products - potentially completely destroying precious items of cultural heritage. This project will focus on archaeological iron from the Mary Rose: Henry VIII's Flagship. Previous X-ray analysis, investigations of a set of iron cannonballs, which have been subjected to different conservation treatments, has informed us on the efficacy of previous treatments, both retrospectively and in real-time experiments, in terms of corrosion products formed. The next step is to develop an understanding of the reaction pathways to the products formed and to investigate the kinetics of these mechanisms as a function of the various conservation parameters (e.g. such as soaking solution, temperature and relative humidity). In addition to individual objects (such as cannonballs), we will investigate how iron deposits in wood behave, with the overarching aim to find viable solutions for conserving notoriously difficult composite artefacts, defined as a mixture of both organic and inorganic materials e.g. an iron fixture in a wooden artefact. To achieve this in-situ cells will be developed so that the corrosion can be monitored in real-time using spectroscopic and scattering techniques. The results will inform future conservation strategies not only for the Mary Rose project, but other heritage project conserving both marine archaeological iron and composite objects

The production and processing of materials accounts for 15% of UK GDP and generates exports valued at £50bn annually, with UK materials related industries having a turnover of £197bn/year. It is, therefore, clear that the success of the UK economy is linked to the success of high value materials manufacturing, spanning a broad range of industrial sectors. In order to remain competitive and innovate in these sectors it is necessary to understand fundamental properties and critical processes at a range of length scales and dynamically and link these to the materials' performance. It is in this underpinning space that the CDT-ACM fits.

The impact of the CDT will be wide reaching, encompassing all organisations who research, manufacture or use advanced materials in sectors ranging from energy and transport to healthcare and the environment. Industry will benefit from the supply of highly skilled research scientists and engineers with the training necessary to advance materials development in all of these crucial areas. UK and international research facilities (Diamond, ISIS, ILL etc.) will benefit greatly from the supply of trained researchers who have both in-depth knowledge of advanced characterisation techniques and a broad understanding of materials and their properties. UK academia will benefit from a pipeline of researchers trained in state-of the art techniques in world leading research groups, who will be in prime positions to win prestigious fellowships and lectureships. From a broader perspective, society in general will benefit from the range of planned outreach activities, such as the Mary Rose Trust, the Royal Society Summer Exhibition and visits to schools. These activities will both inform the general public and inspire the next generation of scientists.

The cohort based training offered by the CDT-ACM will provide the next generation of research scientists and engineers who will pioneer new research techniques, design new multi-instrument workflows and advance our knowledge in diverse fields. We will produce 70 highly qualified and skilled researchers who will support the development of new technologies, in for instance the field of electric vehicles, an area of direct relevance to the UK industrial impact strategy.
In summary, the CDT will address a skills gap that has arisen through the rapid development of new characterisation techniques; therefore, it will have a positive impact on industry, research facilities and academia and, consequently, wider society by consolidating and strengthening UK leadership in this field.