Making Protective Coatings for Bridges, Boats, and the Future
Symposium Organizers: Amelia Nestler, Project Manager at Northwest Green Chemistry; Saskia van Bergen, Green Chemistry Scientist at Washington State Department of Ecology; Lauren Heine, Executive Director of Northwest Green Chemistry
Virtually all manufactured products are protected by coatings, whether they are anti-corrosive, anti-bacterial/anti-fouling, or water/vapor barriers. These coatings provide significant sustainability, environmental, and human health benefits by preventing infection (e.g. antibacterial coatings on implanted medical devices or on hospital surfaces), increasing product life-span (e.g. anticorrosive bridge coatings), and improving performance (e.g. antifouling boat paints help maintain high fuel efficiency). Biofilms—aggregates of microorganisms that adhere to each other, a surface, and/or a self-produced extracellular matrix—drive the need for many of these protective coatings due to their unique resistance to exterior disruption and their ability to cause infection, corrosion, and bio-degradation of materials. A full understanding of the chemistry and biology underpinning biofilm formation and growth is necessary to guide the development of state-of-the-art protective coatings.
Unfortunately, the protective benefits provided by these coatings come at a cost. Many antibacterial and antifouling coatings have significant off-target effects. For example, copper is commonly used for antifouling boat paints, but even low concentrations of copper significantly decrease salmon olfactory senses, preventing salmon from avoiding predators and locating their home stream in order to reproduce, and higher concentrations are toxic to other marine life forms. Many coatings are based on C6 or C8 fluorocarbon technology, and while this does provide a reasonably durable, super-slick coating, the ingredients are persistent, bioaccumulative toxins (PBTs). For some antifouling coatings to function, the antifouling chemical must be released into the environment at a steady leach rate, further complicating the selection of an appropriate durable matrix for the coating. Coatings can interfere with managed end-of-life systems, particularly composting and recycling.
We will open our session with a biofilm expert who will describe the chemistry and biology of biofilm formation and growth, and relate this to current coatings. This will be followed by a case study looking the Washington State Antifouling Boat Paint Alternatives Assessment (AA), framing the session with example metrics for evaluating and comparing both existing and emerging alternatives. From there, we will explore innovations in coatings, including novel nanomaterial-based coatings, coatings based on biomimicry, antibacterial/antifouling chemicals with low off-target toxicity, and disruptive innovations such as ultrasound-based antifouling that could replace some coating needs.