The study of corroded metal objects recovered from historic shipwrecks provides conservators with a unique chance to look at the effects of salts, water movement, depth of burial and the level of dissolved oxygen on the degradation of a wide range of artefacts. Normally the chronology of shipwrecks is well defined and this helps quantify the rates of deterioration that occur. Previous work in these laboratories has concentrated on the identification of corrosion processes and how, through a study of deterioration, we can improve our techniques for stabilising the artefacts (North 1976, MacLeod 1987).

The routine measurement of electrochemical parameters, such as the surface pH of degrading artefacts and the corrosion potentials of metal objects on wreck sites, has a very recent history. Following the early work on the Rapid (1811), corrosion scientists have found that the knowledge obtained through these on-site measurements is an invaluable aid in understanding the corrosion mechanisms and the modes of deterioration of materials on archaeological sites. The significance of this work has only recently been reassessed and shown to be a very powerful tool in not only determining what has occurred over the past centuries but also in providing the practitioner with a rational and non-destructive form of assessment of the inherent archaeological potential of metal objects that are scattered on a wreck site.