Ageing of organic marine coatings and its influence on their mechanical properties and fracture in ballast tanks

Paper in proceeding, 2016

Corrosion concerns and effective corrosion protection of double hull tankers, container ships and bulk carriers have been raised especially in the water ballast tanks (WBTs). Inspections have shown that many coatings fracture earlier than their target design life. This has led to local corrosion of the substrate and unwanted maintenance which is time-consuming and costly for the ship owner. The objective of the current study is to show that ageing of organic marine coatings used in WBT reduces the coatings’ fracture strain to a limit lower than the local strain response of the substrate during normal ship operation conditions. Experimental investigations of three commercial WBT coatings are presented which have been subjected to different types of ageing. Changes in their mechanical properties were confirmed. Finite element analyses of a 4,400 TEU container vessel were carried out for a number of sea state conditions. The strains of the hull structure (i.e. the substrate) were calculated and compared with the fracture strains of the aged coatings. It was shown that, in many locations, the strain of the substrate can exceed the fracture strain of aged coatings. Finally, systematic study with pro-active coating condition performance monitoring is discussed.