16 - Organic coatings for marine and shipping applications

Abstract

Since the maritime environment is strongly aggressive, coatings needed to protect steel can be classifi ed as ‘heavy duty coatings’. In most maritime applications because of maintenance diffi culties a long service life is generally required. This, together with safety and environmental issues, demands high requisites in performance and reliability. On top of performance and reliability requirements for long-term protection, there are often also conflicting interests between the desire of a ship owner or operator for a well-built, long-lasting structure with minimal operating cost (long-term fi nancial interest) and the short delivery time or shipyard’s production line. Depending on the ship building market demand at the time of contract, the owner may have to accept a compromise against his better technical judgement and operating know-how. The extra cost for the desired system may be exorbitant, seen from the owner’s or operator’s point of view, and the standard guarantee for a ship is only one year from delivery, so the yard will rarely face a claim for coating failure if the coating application is reasonably well done. While this may recoup some financial gain in terms of the time-to-delivery of a new structure, there might be a more significant negative impact to the owner or operator in terms of cost of early and on-going maintenance and repairs over the lifetime of the structure. The relative costs of coating systems are minor compared to replacement of steel during operational life. However, costs for staging and steel preparation needed to apply those coatings rise swiftly with increasing surface area. Correct selection of coating materials and their specification at the design stage may yield fi nancial benefi ts in the longer term. Although there are coatings available on the market that perform satisfactorily, and provide long-term protection against corrosion, their reliability is dependent on a strict control of the application, type and thickness of the coating as well as operating conditions. Furthermore, the past 10 to 15 years have shown significant changes in the coating industry. Because of the awareness for the consequences for human health and for the environment, nowadays many regulations and restrictions have been decreed concerning the application, content and removal (waste) of coatings. Many traditional anticorrosive coatings are now no longer acceptable due to their potentially toxic and carcinogenic nature, e.g. red lead, coal-tar pitch, and more. In addition, requirements to reduce emissions to the atmosphere of potential ozone-depleting materials have resulted in a reduction in volatile organic content (VOC) of paints and coatings. Novel coatings should also keep their properties and fl exibility during harsh sea conditions and elevated temperatures at which ships may operate. This chapter will deal with the types of coatings and degradation mechanisms as well as mitigation of degradation of coatings in marine environments and shipping applications in particular.