Analysis of metals recovered from historic shipwrecks provides valuable information concerning the long-term effects of salinity, water movement, and temperature on the corrosion of both ferrous and non-ferrous objects. The corrosion mechanisms for copper and its alloys are shown to be dependent on site location and on the formation of calcareous concretion which establishes a microenvironment significantly different from the ambient sea water. The effects of cathodic protection from surrounding iron objects are discussed in terms of differences in the mineralogy of corrosion products and changes in the corrosion mechanism when the protection ceases. This information can be used as a guide to the provenance of shipwreck material. -- AATA