This project demonstrated and validated the effectiveness of a new environmentally safe anti-fouling coating developed by the Navy. Coating performance was monitored for a period of at least 3 years following application on small (30'-55') U.S. Navy range control boats and U.S. Coast Guard boats in Yorktown, Virginia, and on water intakes in Braden Point, Massachusetts, and Bay City, Michigan. Biofouling has a significant negative impact on the performance of ships, such as increases in fuel consumption and dry docking frequency and decreases in cruising range and speed. Also, industrial and municipal facilities have incurred costs due to the clogging of water intake systems. Traditional methods for controlling biofouling of water intakes depend on the use of targeted chlorination. In addition, ships employ anti-fouling paints that are designed to slowly leach control agents into the water. These methods can pollute the marine environment and threaten water supplies with persistent toxins. Anti-fouling paints also incur significant costs for safe application, removal, and disposal. The new environmental paints that have been demonstrated employ a physical rather than chemical approach and utilize advanced, layered silicone polymers to form minimally adhesive surfaces to which fouling organisms find it difficult to stick.
The new coatings demonstrated acceptable performance when applied to a variety of platforms in freshwater and marine environments. The characteristics evaluated included easy application and adhesion to substrates, durability, ease of repair, and ability to easily remove with a water jet any fouling that did occur. Abrasion resistance of hulls and keels was evaluated on U.S. Coast Guard boats. Installation costs are slightly higher, maintenance costs are expected to be comparable, and disposal costs are lower for silicone foul release coatings compared to the copper ablative coatings they replace. The silicone coatings have experienced up to four years of service with no deterioration in performance. This indicates an effective lifetime at least as good as the conventional toxic coatings and the potential for reducing total life-cycle costs below the $9-12 per square foot range of conventional coatings.
Successful implementation of new anti-fouling coating technology could substantially reduce operating costs for the U.S. Department of Defense as well as U.S. maritime and electric power industries. An effective, environmentally benign coating would reduce Naval fuel costs by 10 to 15 percent ($35 million to $50 million a year) with additional cost savings from reductions in dry docking frequency, remediation of polluted harbors, and disposal of hazardous paint waste.
The duplex silicone foul-release coating systems have been applied in several states and met all local environmental and occupational health standards. When in use, environmental impacts are greatly reduced because the principal mechanism of these anti-fouling coatings is passive. (Project Completed - 1999)