Understanding material interactions in marine environments to promote extended structural life

Corrosion in marine environments is affected by how and to what extent seawater interacts with materials, by the choice of material, and by design of components, systems, and structures. Seawater is a complex, naturally buffered fluid that covers much of the Earth’s surface. The chloride content and the dissolved oxygen content in seawater promote competing processes of passivation and the breakdown of passivity. Seawater is a living medium where microbiological organisms thrive and attach to virtually all materials leading to biofilm formation and micro- and macrofouling. Microbiological activity may accelerate corrosion processes or act as a passive barrier. Biofilms have been shown to ennoble materials in seawater after an induction period.The behavior of materials, particularly metals and alloys, in marine environments generally depend on the chemical composition, the stability of the oxide film, metallurgical and processing parameters, and the effectiveness of any applied protection and mitigation measures.Materials selection and appropriate design can avoid, delay, or minimize the occurrence of several forms of corrosion. The proper choices require an complete understanding of materials, design factors, the type of marine environment, and the relevant corrosion control methodologies in order to promote increasing service life to marine structures.This paper will discuss some of the parameters that affect materials performance and some effective measures by which alloys can be protected in selected marine environments.