Tin-based antifouling coatings have proven an effective and economical means of protecting underwater hulls, but tin has been found to have harmful effects on marine life in coastal areas; it not only keeps algae and barnacles from attaching to the bottoms of ships, but also impacts on other marine organisms. This led to the introduction of a ban on tin for boats under 25 meters in the western world in the 1980s, and work has been under way ever since to develop new tin-free coatings that can improve the environmental performance of larger vessels too. The International Maritime Organization (IMO) is pushing for a complete ban on tin-based antifouling coatings; a draft resolution has been tabled for a complete ban on the application of coatings containing tributyltin (TBT) from Jan. 1, 2003, and for all TBT-based coatings to be removed from all vessels by 2008.
Tin-free products have been on the market for more than a decade, but have not had the desired impact because they simply do not last long enough, and so shipping companies have largely continued to use tin-based products. Second-generation tin-free coatings have a life of more than three years, but even this has not been sufficient to wean the international shipping world off tin.
A third generation of antifouling coatings has been introduced, a generation that is certain to last the required five-year interval between drydockings, and can therefore compete with tin-based products.
SeaQuantum, a tin-free solution suitable for any application, was developed by Jotun in conjunction with Japanese chemicals group Nippon Oil and Fats. “The launch of SeaQuantum heralds a breakthrough in tin-free antifouling systems. Jotun’s new coating has undergone extensive testing and offers up to five years of effective protection against fouling on ship bottoms,” said Stein Kjølberg, marketing manager, Marine Paints. “The new product brings us much closer to meeting the draft IMO resolution that all tin-based antifouling systems should be withdrawn from the market for the next few years.”
Jotun has enjoyed a product and research alliance with NOF for several decades. While Jotun developed the formulation for the actual coating, NOF came up with a silyl polymer that can replace the environmentally hazardous tin compounds used in today’s self-polishing antifouling coatings. Silyl polymers are already used in a variety of products, including food additives, dental materials, and artificial organs.
Although tin-free alternatives have been available for several years, none has lasted long enough to meet the shipping sector’s need for five-year systems. Most last for just three years, and cannot provide the same self-polishing effect that tin-based coatings achieve. SeaQuantum, however, is self-polishing and has almost identical physical and chemical properties to tin-based antifouling coatings. This means that it combines protection against fouling with a hydrolysis reaction that makes the ship’s bottom increasingly smooth as the coating wears, and so makes the ship more and more efficient.
The new coating has undergone no less than seven years of testing, and Jotun can reference tests and practical experience on more than 500 vessels. On the strength of this extensive body of material, Kjølberg said that the coating could be the most advanced tin-free marine antifouling system on the market.
The active antifouling ingredient in the coating is a copper compound. “In the long term, we expect the copper content to be reduced, and maybe replaced entirely with other substances,” he said. “This has not been possible as yet, but is one of the challenges faced in the development of the next generation of antifouling coatings.”
Jotun recommends SeaQuantum for new builds and full-bottom upgrades. When it comes to maintenance drydockings for minor patch-up work, Kjølberg recommends other products developed as part of the new product range.
The new tin-free antifouling coating is more expensive than today’s tin-based systems; prices depend on the type of coatings, but can be three or four times higher per liter. However, he says he does not expect prices to prove a serious barrier to a switchover to tin-free products. Not only can the cost of a coating never be based on price per liter alone, coatings also account for a relatively small share of the overall cost of a five-year drydocking. Furthermore, Jotun can offer tests demonstrating that the system brings savings in fuel costs relative to other tin-free technology available today — fuel consumption was reduced by 15% after two years in a full-scale test. SeaQuantum can cut fuel costs in this way because the bottom of the ship becomes increasingly smooth as the coating wears, thereby reducing friction as the ship glides through the water. Added benefits include lower emissions of greenhouse gases and a decrease in the strain placed on the vessel’s propulsion machinery.
Jotun says that, when used in conjunction with the company’s application program, the material can cut both drydocking times and the consumption of coatings. The company also can demonstrate that this results in less waste, making for clear benefits in terms of both financial and environmental considerations.
The new coatings in the SeaQuantum range will initially be produced at Jotun’s coatings factories in the United Kingdom, the United Arab Emirates and Singapore, and will be available through the company’s global network.