Hundreds of years ago, sailors realized the benefits of using copper to reduce marine growth on wooden ship hulls. Before copper, hulls fouled rapidly, reducing speed and inviting marine worms to devour boats. Fiberglass, steel and aluminum have replaced wood as primary boat-building materials, but copper remains the preferred anti-fouling agent.
Just as hull materials changed over time, bottom paints are about to change. Water-quality studies throughout California, the East Coast and Europe indicate elevated levels of dissolved copper in most marinas. California has established a very low threshold for copper toxicity, so alternative bottom paints are being broadly tested.
There are currently two approaches to alternative bottom paints: nontoxic (super slick) and zinc. The nontoxic alternative to copper is to make the surface so slick that marine organisms have difficulty attaching to it. Preliminary tests indicate that vessels operating at high speeds can knock off any marine growth. What’s left can be wiped off with a soft cloth. Although zinc, like copper, is also toxic to the type of marine organisms that attach to hulls, the threshold for toxicity is higher than copper’s. Some prominent paint manufacturers are offering zinc-based bottom paints as an alternative to copper-based paints.
Santa Barbara Harbor is hosting the next round of research on noncopper bottom paints. California Sea Grant and UCSB have installed experimental panels throughout the harbor painted with various noncopper bottom paints. Researchers will monitor the panels regularly for a year to determine growth rates on different paints. In addition, Santa Barbara Channelkeeper is conducting a unique experiment in which four different noncopper paints have been applied to the hull of its boat in the Harbor.
Finally, the Waterfront Department will soon apply noncopper bottom paint to one of its patrol boats. Between the Sea Grant/UCSB research, the Channelkeeper experiment and the patrol boat experiment, identifying a noncopper bottom paint that works best for our harbor may be right around the corner.
Karl Treiberg is the Santa Barbara Waterfront Department‘s waterfront facilities manager.