9 - The corrosion of metallic artefacts in seawater: descriptive analysis

Abstract

Publisher Summary This chapter highlights that corrosion is the result of interactions between a metal and its environment. Seawater is a very complex medium characterized by the variety of its elements, which are either chemical (water, ions, gases, etc.), mineral (carbonates, silicates, etc.) or biological. They interact to create, on a metal surface, a very complex and corrosive medium. Because of this complex chemistry and intense biological activity, all seawater is a very corrosive environment for immersed materials. The chapter examines, through the description of seawater parameters and through the burial chronology of heritage artefacts, the corrosion forms and hence the corrosion products that can grow on archaeological artefacts in seawater. It describes the major corrosion products encountered on iron, copper, lead, and tin alloys. It focuses on the formation and growth of corrosion products on iron-based alloys. It evaluates the physicochemical seawater parameters in these corrosion processes and describes the kinetics of iron corrosion product formation and growth, their link with the physicochemical parameters and biological activity, and the relationship with the environmental conditions of burial. It also describes the corrosion products observed on other metal surfaces and reviews the relationship between the growth of these corrosion products and the difficulties observed in conservation and restoration laboratories.