Abstract
Marine coating systems installed aboard commercial and military vessels are exposed to extremely aggressive environmental conditions during maritime operation.
A key element in prolonging the useful life of any ship, both commercial and military, lies in the selection and installation of cost-effective corrosion control methods and materials at newbuild, followed by an effective painting and preservation program to minimize the corrosive effects of operating in a marine environment, extend the service life and maintenance requirements of the installed systems, and thereby reduce the total operating cost (TOC) for the vessel.
This paper provides guidelines for calculating approximate installed costs of coating systems, expected coating service lives for each system identified, and methods for determining the most cost-effective systems to use, the effect of maintenance sequences on long-term costs and system performance is also reviewed.
The analysis utilizes trade studies from coating manufacturers, scholarly papers, technical reports, engineering studies and specifications from maritime and naval sources, and technical and consensus organizations that focus on the design, implementation, and testing of marine coating systems.
New coating technologies that show promise of providing enhanced corrosion protection are identified and their relative contribution to lowering the operational costs of shipboard systems are demonstrated through the use of software programs that predict coating service life and maintenance requirements following initial installation.
Corrosion is the silent stowaway that travels on every ship, regardless of their design or nature of maritime service. A key element in prolonging the useful life of any ship, both military and commercial, lies in the selection and installation of cost-effective corrosion control methods and materials during initial construction, followed by an effective painting and preservation program to minimize the corrosive effects of operating in a marine environment.
Marine coating systems installed aboard commercial and military vessels are exposed to extremely aggressive environmental conditions during maritime operation. They include exposures to: seawater, freeze/thaw cycling, the ultraviolet component of sunlight, mechanical damage, stack exhaust, temperature extremes, erosion, and more.
Marine vessels, whether they are in commercial or military service, contain common elements in their construction. These areas include: topsides and superstructure, deck, interior crew spaces, cargo hold, cargo tanks, ballast tanks, and underwater hull.
Coating manufacturers, commercial shipping consensus organizations, and the international military community have identified paints and specialized coating systems with superior performance, durability, and economic effectiveness for maritime service.i,ii Important factors like ship mission, operating schedules, areas of operation, and drydocking intervals for maintenance will also influence the selection and type of coating system to be applied.
With the development of high strength steels, scantling dimensions have been reduced to lower the weight of vessels to reduce fuel consumption. However reduced plate thicknesses have increased the potential of structural failure through corrosion.
Coating selection will also impact the cleaning and painting requirements for the shipboard maintenance of painted surfaces. Additionally, the corrosion the protective coating systems over various substrates have also been evaluated. These factors have been considered during the course of this study.
Coating repairs at sea are regarded as temporary and when detected, only made to avoid component failure before laying up the vessel for depot repairs. For instance, ballast tanks cannot be inspected unless they are drained and cleaned. These operations are typically performed when the vessel is in for shipyard or depot repairs.
Over the past 40 years, new technologies in protective coatings and preservation systems for marine applications have been developed that show promise of providing greater corrosion protection and reduced maintenance. A plethora of data exists in such information sources as: trade studies from coating manufacturers, scholarly papers, technical reports, engineering studies and specifications from such organizations and agencies as: Naval Sea System Command (NAVSEA), Office of Naval Research (ONR), department of Department of Defense (DoD), US Bureau of Ships, National Association of Corrosion Engineers (NACE) Symposia, Marine industry Symposia, Military Sealift Command (MSC), International Maritime Organization) IMO, National Institute for Standards and Technology (NIST), American Bureau of Shipping (ABS), U.S. Corps of Engineers, American Society for Testing and Materials (ASTM), International Standards Organization (ISO), and the Society for Protective Coatings (SSPC).
Existing statistical methodology was used to develop information relative to the prediction of coating service life and maintenance requirements following initial installation. A principal source in this area was data published by the SSPC and NACE.
