Virginia Beach, VA. June 5 to June 7, 2000An Overview of New Antifouling Technology Dr. Geoff Swain, Florida Institute of Technology
Virginia Beach, VA, June 7 Dr. Geoff Swain spoke about new antifouling technologies that his research team from the Florida Institute of Technology has been studying. He
said there is an extraordinary amount of new technology coming out and shippers are most interested in which will be the most productive. Swain explained the parameters
by which a successful antifouling technology is determined. He then described a number of currently available systems and their merits or disadvantages.
The "ideal" technology, explained Swain, would be long lasting, hydraulically smooth, non-corroding and cost effective. In reality the two most critical factors are hull
roughness and fouling. The rougher the coating, the greater the loss in performance and biofouling, in itself, creates hull roughness. Swain explained that every 10 microns
of roughness equates to a loss in performance of 1%. An optimal coating may create about 22-80 microns in hull roughness. Biofouling can increase that to 200 microns in a very short period of time.
Self Polishing Coatings -
Self polishing coatings were developed in the 1960's and
provide excellent performance since they keep smooth via the process of self polishing. Organotin self-polishers were and are the most popular coatings because they are the best current technology to combat hull
roughness at a low cost, says Swain. However their environmental performance is questionable, and we are entering an age where we are all considering more and more of the
environmental implications in the technologies we will be using.
Copper self polishers are still popular today thanks to their less noxious environmental
properties such as low bioaccumulation. Swain points out that copper is an essential element for normal growth. The disadvantage of copper self polishers is their release
rate is affected by pH, salinity and temperature, all of which are key aspects of a ship's operational environment. Copper coatings all require booster biocides and the
challenge in using a booster biocide is how to control the release rates.
Tin-free polishing systems are mainly organic booster biocide driven. Swain says to
watch organic booster biocides to be the main ingredient in new coatings. The FIT group has seen the most success with Zinc Pyprithione and Sea-Nine 211. He notes the
problem with any self polishing system is, ships will still be contributing large quantities into the environment.
Natural Antifouling Mechanisms -
Chemical Inhibitors Some antifouling systems are using naturally produced biocides from bacteria, plants and animals. The difficulty is incorporating the naturally
produced inhibitors into the paint for transition to use on ships.
Non-Stick Coatings Swain pointed out that FIT is doing
much research in the area of non-stick surfaces for marine use. Researchers have been studying marine organisms such as dolphins and sharks to see why they do not have fouling problems, yet other organisms such as manatees
do. By looking at the surface properties of dolphins and sharks, scientists are hoping to gain some knowledge about what properties are successful.
Swain first noted that there is no such thing as a non-stick marine surface. The technologies in use today work by fouling and release.
According to Swain, the critical factor in non-stick coatings is adhesion. FIT studies have shown the most successful surface will be one that reduces adhesion below the
level where the force of water to release the fouling will be less then 5 psi. The best coatings will have an adhesion factor below 1-2 psi. This means little force is required to release or "knock off" the fouling.
Silicone coatings such as RTV11 and others are under testing at FIT. Swain said their advantage is there is no known environmental damage from these coatings. The disadvantages are:
- They are expensive.
- The coatings are weaker and more vulnerable than other surfaces hence they are more easily damaged in a shipping operational environment.
- Proper application in the correct environment is the KEY to success.
January 2003 Deadline
Whether or not a full arsenal of effective new antifouling technologies will be available in the near future, Swain was unable to say. He pointed out however that to meet the
January 2003 deadline for the ban on organotin paints, much more funding must be made possible. A lot of research from a community of teams must be performed to
thoroughly evaluate the critical problem of marine biofouling.
The National Paint and Coatings Association International Marine and Offshore Coatings Conference: Virginia Beach, VA. June 5 to June 7, 2000