Understanding the long-term corrosion mechanisms of iron in an anoxic environment is essential in the field of the preservation of archaeological heritage artefacts and nuclear waste management. Corrosion mechanisms have been assessed by examining nails 400 years old from the archaeological site of Glinet. This chapter provides an overview of the characterisation of the entire corrosion system environment/samples through coupled multiscale analytical tools. The environment is anoxic, calco-carbonated and water-saturated. Three corrosion patterns composed of ferrous carbonates (siderite and chukanovite) and magnetite have been identified. Depending on the connection between the phases and their location, the electronic properties of the corrosion layers have been established. The electrochemical behaviour of the corrosion system shows that water reduction at the metallic interface is negligible. Furthermore, the electron consumption sites are mainly localised on the external part and the precipitation sites on the internal part of the corrosion layer. The corrosion rate is estimated to be less than 2μm/year and a corrosion mechanism is proposed based on a decoupling of the anodic and cathodic sites and on the existence of a nanometric corrosion layer at the metallic interface.
Oxygen is a key factor in corrosion and decay of artefacts from our cultural heritage. The measurement of oxygen concentrations and quantification of oxygen consumption is therefore extremely useful in both corrosion and conservation science. This chapter focuses on two aspects of oxygen monitoring: first, measurement of oxygen consumption of cultural heritage artefacts to evaluate their corrosion rate and the efficiency of conservation treatments, and second, measurement of oxygen concentration in the burial environment to evaluate the preservation conditions and understand the formation of different corrosion products in situ. The chapter includes a short description of equipment for oxygen measurement, and gives some examples of its use for monitoring purposes.
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