International. In a double benefit to the global economy and global climate, Evonik confirmed that it plans to make ship hulls invisible to microorganisms and thus protect them against biofilms, algae and bivalves.
Growths of this type, known as biofouling, increase fuel consumption in maritime transport and, therefore, also CO2 emissions in the world's oceans. The International Maritime Organization estimates that the annual costs caused by biofouling are in the range of billions of dollars. Evonik is working on a solution to the problem in the form of new eco-friendly coatings that counteract biofouling. The coating tricks microorganisms into perceiving the simple water in front of them, rather than the ship's hull; as a result, they often do not try to settle into the helmet.
Biological contamination has long been a problem for shipping companies around the world: organisms settle on the ship's walls, turning smooth surfaces into a rough, uneven shell. This increases the friction resistance in the water, so biofouling decreases the speed of the boats. These need more energy to maintain their speed, which is bad news for both fuel costs and the environment. Shipping accounts for about 90 percent of global freight transportation.
"Biofouling is one of the last unsolved problems in the coatings industry. Up to this point we had not been able to find the optimal solution for ship casings that were efficient and environmentally friendly. This is why antifouling coatings are a central theme in our new 'Smart Surface Solutions' Competence Centre," says Stefan Silber, Director of Innovation Management Coverage Additives in Evonik's Resource Efficiency Segment. The work of the experts here is not limited to marine coatings; it also covers topics such as ice protection, antimicrobial coatings and dirt-repellent surfaces.
To protect ships' hulls against biofouling, Evonik scientists are exploiting a trick in the new coating: in it, they combine a water-repellent (hydrophobic) silicone with a water-loving polymer (hydrophilic). This results in the formation of amphiphilic polymers, in which hydrophilic and hydrophobic domains alternate. Hydrophilic domains attract water to the hull of the ship. This builds a kind of shell of water around the polymers, camouflaging the hull of the organisms. Alternation with water-repellent domains further confuses organisms: they can no longer clearly recognize the surface, nor distinguish the hull unequivocally from seawater. As a result of this uncertainty, they are usually kept away from the helmet.
If microorganisms try to settle in the hull, the second defense mechanism of the hydrophobic domain – its non-stick action – must come into play: the base material for the new solution against biofouling, the hybrid silicone resin Silikopon EF from the Evonik portfolio makes it difficult from the beginning for organisms to settle in the helmet. This is because the low surface tension and extremely smooth surface of silicone give it easy-to-clean properties. Organisms cannot easily adhere to the hull, and the few that do so must be dislodged by the stream of water, even at low speeds.
"We are using a tested and tested product in a new way and at the same time expanding Evonik's expertise. So we are succeeding in developing new solutions for coatings to protect ships against biofouling and without attacking organisms directly," says Silber.
The researchers are making good progress in developing their innovation: field tests under real conditions have already demonstrated the basic efficacy of the new hybrid systems. The scientists are now working together with industry customers on coatings based on the new systems.
They are also confident that they can increase the interval between successive applications of the coating in the future. This would allow shipping companies to reduce maintenance costs as well as the negative effects of biofouling, such as high fuel consumption.
