The routine measurement of electrochemical parameters such as the surface pH of degrading artifacts and the corrosion potential of metal objects on wreck sites has a very recent history. Following the early work on the <i>Rapid</i>, (an American China trader lost off the Western Australian coast in 1811), conservators 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 using data recorded on the HMS <i>Sirius</i> site and shown to be a very powerful tool in not only determining what has occurred over the past centuries on a maritime site, but it also provides the practitioner with a rational and nondestructive form of assessment of the inherent archaeological potential of metal objects that are displayed on a wreck site. The use of sacrificial anodes to pretreat artifacts on the sea bed is discussed and the benefits are rationalized.