Strip or seal?

Now that the IMO has decided to allow owners to seal-in TBT antifoulings instead of removing them altogether, the question is; how do you go about getting it done? While the legislation is new, the problem is not. Paint companies say that they have been tackling this problem for a while as owners have been switching from TBT to tin-free products. While the development of specialised sealers is an option, many paint companies are adopting a wait and see approach before spending large sums of money on R&D before the final regulations governing the sealer coats are developed. Claes Skat-R?rdam, global product manager for Hempel?s Marine Paint says, “We have sealers that, in our internal leach tests, show to be effective. However there has not yet been established an IMO approved test method ? for those two reasons, we are not promoting the sealers? yet.” It has been pointed out to The Motor Ship that many coatings will seal antifoulings as long as they will adhere to the surface and offer a good surface on which to apply the new antifouling. Topside coating accidentally spilt on antifoulings, for example, is enough to render the antifouling inactive and therefore prevent it leaching. However, Dr David Arnold, Jotun?s technical manager, says, “The substrate should be sound and subject to good adhesion.” He explains that everything should be carried out using good painting practice, making sure that the sealer is compatible with both the new antifouling and the existing ones. Proposals had been put forward that TBT antifoulings just be overcoated with tin-free products, but as Linda Diamond, Jotun Henry Clark?s marketing service manager, points out, what happens if a charter is extended beyond a ship?s normal drydocking? The tin-free antifouling is likely to leach away leaving the unsealed TBT antifouling to be subjected to leaching and reactivation. Third option However, Hempel has come up with an option that many might not have considered ? a third option, which Joern Kahle, the company?s marine sales manager, tells The Motor Ship, “We haven?t seen anything that prevents it.” He explains that it is suitable for vessels that will be drydocked twice before the January 1, 2008 deadline. In the first drydocking any TBT antifouling can just be overcoated with copper-based coating and the decision as to whether to seal or strip left until the second drydocking. It is for this reason that Skat-R?rdam says “We expect the demand for sealers to raise sometime during 2006 or 2007 ? the reason being that it is not until January 1, 2008 it is required to have old TBT sealed off.” Diamond told The Motor Ship that owners who keep their vessels for a long time will have to have them stripped off at some point and that ships are likely to be stripped back to bare metal at the second or third drydocking. But if the vessel is damaged it might be a good opportunity to have the TBT removed altogether. If owners go for sealing, Arnold warns that it is almost impossible to prevent all TBT contamination as there is likely to be ships that have anchor or chain damage that penetrates the sealer coat exposing the TBT. However, he says that in the scale of things, this will be minute. So, presently, there appear to be few sealers that have been designed specifically for the purpose of sealing in TBT antifoulings, with paint companies adopting a ?wait and see? approach. The exception is International?s Intersleek 717 Linkcoat, which has been designed to allow TBT self-polishing antifoulings to be overcoated with the company?s Intersleek foul-release system. n