Erosion–Corrosion-Resistant Coatings for Seawater Piping Components—A Review

Seawater piping systems and their associated components such as pump, shafts, and valves in naval warships suffer from severe erosion–corrosion in their valve seats, pump impellers, and pump casings thereby leading to higher failure rates. As a result, they are a continuing maintenance burden to both ships' forces and repair activities. The need to reduce both maintenance costs as well as recurrent high dry-docking costs of ships has necessitated development of advanced materials and coatings for long-term reliable service in aggressive marine environments. Commercially available metallic powders containing cemented carbide grades are generally used in applications requiring erosion–corrosion resistance surfaces for enhanced performance. In these, the binder phase has been specifically designed to increase corrosion resistance to a level exceeding that of the grades that contains cobalt alone as the binder phase. Further, variations of cemented carbides with other alloying elements such as NiCr and others as well as recently developed amorphous metallic powders are being explored by thermally spraying them on cheaper substrates for enhanced erosion–corrosion resistance in seawater piping applications. In this paper, the various materials and coatings developed by the researchers and scientists over a period of years to combat erosion–corrosion problems and their behavior in chloride bearing aggressive seawater environments are reviewed along with futuristic approaches and directions for development of high-performance erosion–corrosion-resistant coatings for marine environments.