Antifouling Coatings for Invasive Mussel Control
Project ID: 7095
Principal Investigator: Allen Skaja
Research Topic: Invasive Species
Priority Area Assignments: 2010 (Zebra and Quagga Mussels), 2011 (Zebra and Quagga Mussels), 2012 (Zebra and Quagga Mussels), 2013 (Zebra and Quagga Mussels), 2014 (Zebra and Quagga Mussels), 2015 (Zebra and Quagga Mussels)
Funded Fiscal Years: 2010, 2011, 2012, 2013, 2014 and 2015
* What coatings will provide long-term, mussel-free service?
* What coatings will provide excellent corrosion protection and durability and deter mussel attachment?
Need and Benefit
One promising method to control mussel infestations on the Bureau of Reclamation's (Reclamation) infrastructure is to use coatings that prevent fouling by mussels on trashracks, intakes, and piping that are at high risk for blockage from mussels. Currently, chemical treatment (chlorine) is the most widely used method for control. However, chemicals require discharge permits to release into open waters, and using chemicals is not practical in all situations. Ontario Hydro has reduced the amount of chemicals it uses by applying antifouling or foul-release coatings to critical infrastructure.
Antifouling coatings are toxic to the fouling organisms and leach biocides into the water. Cuprous oxides and chemical biocides are normally the biocides used in antifouling coatings. Biocide leach rates depend on water chemistry, pH, water temperature, and flow rates.
Foul-release coatings are based on surface properties (chemistry) to deter the attachment of fouling organisms without releasing toxins into the water. These types of coatings do not depend on water chemistry, pH, temperatures, or flow rates. The majority of foul-release coatings are formulated with silicone elastomers such as poly(dimethyl siloxane) (PDMS). Unfortunately, typically these coatings are soft and not very durable. Currently, we have tested three foul-release coating, and only two are still performing well after 13 months.
The use of fluorinated powder coatings was studied under the fiscal year 2009 research project. These have never actually been tested for antifouling properties; however, the Naval Research Laboratory (NRL) has tested similar polymers with barnacle adhesion. Past NRL research and technologies may actually work for mussel control, whereas the technologies did not work for all fouling organisms and were abandoned by the Navy. The samples coated with fluorinated powder coatings are mussel free after 6 weeks of immersion. These coatings are much more durable than the typical foul-release coatings. Further research and evaluation is needed to determine the effectiveness of these products.
Currently, we are finding that about 90 percent of the products we have tested are not performing according to manufacture claims. The failure rate is very high and is too high for our limited budget to keep testing every coating that a manufacturer recommends. One of the problems has been that the testing procedures set by industry are not acceptable for our exposure conditions. It appears that the testing has always been done in static exposure, while our intakes and trashracks are in dynamic exposure.
Before coatings are selected for full-scale testing (immersion in actual field exposure), they need to be prescreened to determine the likelihood of success for mussel control. It is very expensive to test a company's product based on the company's assessment of the suitability of their product for mussel control. Many times, the companies have no experience relative to using coatings for mussel control, so we end up subsidizing their product development testing. Suppliers of coatings need to provide data to show that their materials have some chance of providing mussel control before we perform testing. We have been conducting testing in both static and flowing service conditions and have found that coatings last longer in static conditions compared to flowing conditions, which is probably due to biocide leach rates. At this time, Metropolitan Water District of Southern California (MWD) and Reclamation are the only two agencies within the United States and Canada that are testing coatings in dynamic exposure conditions.
Bureau of Reclamation Review
The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.
Coatings for Mussel Control - Three Years of Laboratory and Field Testing (interim, PDF,
By Allen Skaja and Dr. David Tordonato
Report completed on June 14, 2012