6: Metals

The focus of this chapter is metals in art and heritage collections, from native metals to contemporary alloys, their properties, corrosion and conservation, with reference to the analytical techniques used to facilitate their study and long-term preservation. It includes a short introduction to the use of metals and how alloying alters their working and performance properties. The variability in composition and properties also affects the way objects corrode. Corrosion of a metal is the result of its interaction with its environment resulting in irreversible changes to the chemical, physical and mechanical properties of the material. These changes can result in a wide variety of effects. Different environments, such as soil-based, atmospheric or marine, will be discussed in relation to these corrosion phenomena. Analytical techniques are divided into those which can provide information about the chemical composition and structure of an object (metallography, XRF, SEM–EDS, etc.), and those which provide information about the extent and type of corrosion (e.g. X-ray imaging, XRD, Raman spectroscopy), all of which facilitate conservation treatments. Analytical methods are valuable tools in conservation. Basic conservation approaches and factors affecting them are also discussed.