“We all pay for barnacles”
Marine antifouling paints are in a constant state of development, Marine Technology Consultant Jerry Bohlander told delegates at the Biosecurity Summit.
Mr Bohlander, a former ocean engineer with the US Navy, said marine fouling was estimated to cost the US Navy US$10 million to US$25 million a year in fuel losses because of increased hydro-dynamic drag. It was an issue for all ships, but there were particular issues for the Navy relating to the length of time ships spent in port and on short local operations.
He said practically everything had been tried to find coatings to protect ship hulls from corrosion and marine fouling accumulation. The primary fouling control method remained copper-based antifouling paints and underwater hull cleaning by divers and cleaning machines.
Mr Bohlander said the US Navy had an aggressive testing programme to find low or non-toxic paints that provided better antifouling performance and environmental compliance.
Ablative cuprous oxide antifouling paints typically provided from 18 to 40 months or more of protection from calcareous (barnacles, mussels etc) fouling attachment. Performance is related to a ship’s operational cycle, the time of year and location.
Fouling could increase fuel consumption by as much as 8–12 percent for biofilms (the initial slime layer that fouls a vessel’s hull) and up to 24 percent and more for calcareous forms. Propellers were especially vulnerable (bare bronze had no protection from fouling), and fouled propellers could increase fuel consumption by 6–14 percent.
Mr Bohlander said efforts were underway by the US Navy to test and evaluate commercial silicon non-toxic paints, currently in use on several hundred commercial ships, on hulls and propellers. However, silicon paints required sustained speed to self-clean and might require specialised cleaning.
He said each of the underwater hull coating materials and processes being investigated had its own life cycle, cost and environmental issues that needed to be addressed. Most had biosecurity benefits in that they would reduce translocation risk of fouling and associated organisms, either on their own or in combination with appropriate maintenance processes.
Mr Bohlander is an ocean engineer who recently retired from the Carderock Division of the Naval Surface Warfare Center, a US Navy laboratory near Washington DC. He is now a marine technology consultant. For 35 years Mr Bohlander was involved in research and development and project management in the area of antifouling and anticorrosive coatings, shipyard preservation processes, environmental issues and underwater hull maintenance systems. He pioneered the use of remote automated underwater vehicles for ship hull evaluations and maintenance planning, and he acted as project leader for the development of advanced environmentally compliant underwater hull cleaning systems and robotic systems for the application of ship hull paints in dry dock. He is a recipient of the Navy Meritorious Civilian Service Award.
Page last updated: 8 January 2009