Smart Coatings: Evonik Creates an Invisibility Shield on Ships

• New coating technology makes ships invisible to microorganisms

Evonik, delivering dual benefits for the global economy and world climate, plans to make ship hulls invisible to microorganisms and thereby protect them against biofilms, algae and bivalves. Microorganism formations of this type, termed biofouling, increase fuel consumption in maritime shipping and thus also CO2 emissions in the world's oceans. The International Maritime Organization estimates that annual costs caused by biofouling are in the billions of dollars range. Evonik is working on a solution to the problem in the form of new environmentally friendly coatings that prevent biofouling. This new coating technology is based on microorganisms being unable to perceive the ship surface and seeing it as water instead, so microorganisms do not attempt to settle on the ship surface. Biofouling has long been a problem for maritime shipping companies worldwide: organisms settle on ship walls, turning smooth surfaces into hard and rough shells. This increases friction resistance in water, with biological degradation slowing ships down. Ships consequently require more energy to maintain their speed, which increases fuel consumption costs. Maritime shipping accounts for approximately 90 percent of global cargo transport.

"Biofouling is one of the last unsolved problems in the coatings industry. Up to this point, we have not found the most suitable solution for efficient and environmentally friendly coatings" said

Stefan Silber, Head of Innovation Management Coating Additives in the Evonik Resource Efficiency Segment, and added "Toxic paint coatings are one of the main topics of the new 'Smart Surface Solutions Competence Center.' The work of experts here is not limited to marine coatings; it also covers topics such as anti-icing protection, antimicrobial coatings and non-stick surfaces." Evonik scientists have developed a "deception" for microorganisms in the new coating to protect the ship hull against biofouling. A water-repellent (hydrophobic) silicone is combined with a water-loving (hydrophilic) polymer. This results in the formation of amphiphilic polymers with alternating hydrophilic and hydrophobic regions. Hydrophilic regions bring water to the ship. This creates a kind of water shell around the polymers and camouflages the hull from organisms. The alternation with water-repellent regions makes things even more difficult for microorganisms, no longer recognizing the surface clearly or being unable to distinguish the hull distinctly from seawater. As a result of this ambiguity, they typically keep their distance from the hull. Should microorganisms still attempt to settle on the ship, the second defense mechanism of the hydrophobic region, namely its adhesive effect, should come into play: the basic material of the new biofouling solution in Evonik's portfolio, SILIKOPON® EF silicone hybrid resin, makes it difficult for organisms to settle. This is because silicone has very low surface tension and extremely smooth surface properties. Organisms do not easily adhere to the ship, and the small number of microorganisms that do succeed are removed by water movement even at low ship speeds. Stefan Silber concluded "In this way, we are using a tried and tested product in a new way and at the same time expanding Evonik's expertise as well. Thus, we are succeeding in developing new solutions for coatings to protect ships against biofouling and can do so without directly attacking the organisms." Researchers are making good progress in developing their innovation. Field tests under real conditions have already demonstrated the basic effectiveness of the new hybrid systems. Scientists are now working with customers in the industry on coatings based on the new systems.