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The Copper Conundrum: Do Other Anti-Fouling Paints Work as Well?

July 18, 2013

From science.gu.se. Photo by Mats Hulander, University of Gothenburg.

For the past decade, copper has been the go-to metal to prevent boat hulls from fouling. A biocide, copper kills or deters marine life from sticking to boat bottoms. But studies suggest that copper, like its predecessor tributyltin (TBT), damages aquatic systems and species even at low levels like 2 ppb. In poorly circulating bays and marinas, copper reaches much higher levels. In San Diego’s Shelter Island Yacht Basin, an estimated 2.5 tons of copper leaches from the bottoms of 2,000 boats each year.

Western states are leading the campaign against copper bottom paints. A state of water conscious citizens, Washington became the first state to ban copper based paints, though this ban hasn’t yet taken effect. Beginning in 2020, owners of recreational boats (under 65 feet) cannot buy bottom paint that contains over 0.5% copper. And starting in 2018, recreational boats on the market need to be stripped of copper paint or sealed. In California, a similar bill to ban copper paints in recreational boats has been shelved in the Senate until later this year.

If you’re a marina manager, boatyard employee, boat painter, or simply a boat owner, it may be time to look for a new anti-fouling paint. What other options exist for those that want to do minimal harm to aquatic species without sacrificing cost and performance? Dr. Katy Wolf of the Institute for Research and Technical Assistance (IRTA), has made it her goal to find out. Wolf conducted a series studies at West Coast ports and boatyards to determine both the highest performance non-biocide paints, and the most cost-effective application methods.

A joint study between the Unified Port of San Diego and IRTA found that a number of non-biocide paints performed as well, or better, than copper paints. A few of these, for interested boaters, are: Intersleek 900, Hempasil X3, and BottomSpeed. This study suggests that non-biocide paints are currently more cost-effective than copper paints if one considers the value over the lifetime of the paint. Soft non-biocides require cleaning and maintenance costs comparable to copper paints, and they last longer – up to ten years vs. an average of around three years for copper paints.

Some current copper replacements use zinc biocide or zinc-oxide paints. But Wolf fears that the convenient replacement of one metal for another will prove short-sighted. “Replacing one biocide for another doesn’t solve the problem,” Wolf said in a recent webinar hosted by the Western Sustainability and Pollution Prevention Network (WSPPN). “It’s better to move directly to non-biocides.” As with copper, studies suggest that zinc has significant toxicity to marine life and should be regulated just as closely as other heavy metals. Non-biocide paints, on the other hand, do not pose the same risk to marine and human health. “There are some excellent non-biocide paints out there,” said Wolf. “But we need to develop more.” Some creative biomimetic technologies are in the works (as the one profiled by this NPR story), but development of non-toxic paints and glues is still a young and open field.

Although non-biocide paints are almost certainly less toxic than biocide paints, we do not know much about the toxicity of newly developed non-biocides. One limitation of Wolf’s paint comparison studies is that funding did not cover the testing for aquatic toxicity of replacements for copper paints.


Instead, Wolf analyzed cost comparisons between copper paints and their replacements. One problem with non-biocides, she found, is that they require higher initial costs than copper paints. According to supplier instruction, applying non-biocides generally requires stripping the hull for the first paint application. Hull stripping costs about five times more than simply applying an overcoat of copper paint.

Therefore, Wolf has recently turned her attention to minimizing the application costs of non-biocides. A few simple solutions show significant promise. Primarily, the option to apply non-biocide over an existing copper paint job would drastically reduce painting costs. But Wolf suggests that we need more research to determine the feasibility and safety of this option.

In addition to looking at alternative paints, Wolf also examined some creative hull stripping methods that were far less toxic and polluting than the standard chemical stripping or dry sanding methods currently used by most boatyards. As an alternative to stripping hulls with the possible carcinogen methylene chloride, Wolf suggests using soda blasting or dry ice blasting. These methods are much less toxic and cost about the same.

Wolf also looked at the possibility of recycling copper from dry sanding operations. One pilot study suggested that boat yards can profit from the copper hidden in their shells. A California boatyard yielded valuable dust from dry sanding hulls. This dust, considered hazardous waste in California, contained up to 60 percent copper. Instead of paying a $2,400 waste fee to dispose of the hazardous waste, the boatyard sent the waste stream to a recycling center that paid for the metal.

Wolf’s studies suggest that some good alternatives to biocide paints already exist. But Wolf recommends that we need more studies to better determine safe and appropriate paints for different environments, and different types of boats. For Northwest residents, the time is now to start thinking about alternative paints and stripping methods. Copper isn’t welcome in our waters anymore. Which alternative paints work best in our colder waters? Are Dr. Wolf’s results transferable to our waters? How else could paints or stripping methods be improved?

The rest of the boating nation will be watching to see what and how we do.

Additional Resources

– By Cyrus Philbrick

Communications Manager


2 responses to “The Copper Conundrum: Do Other Anti-Fouling Paints Work as Well?”

  1. My name is Emiliano Pinori.
    I wonder why the use of my picture (top of this article the boat test result) without mentioning what that picture represent. It is the result of my research leading to a PhD thesis, a EU founded project LEAF and more importantly to one of the few possible alternative to copper in the near future by a low-buget and feasible approach. The Low Emission Anti Fouling (LEAF) means organic no-leaching biocide working by contact, read more on the link where the picture was taken http://www.science.gu.se/english/News/News_detail/boat-owners-can-fight-barnacles-with-new-eco-friendly-method-.cid1175568
    With the help of EU founding and 7 different partners all over the Europe and Brazil, we are now going to push furthwer this concept from low release to zero release http://www.leaf-antiffouling.eu . I hope that i a near future we could replace the copper with smart use of biocide or even better (when cost will be lower) with no biocide at all, but, fouling release paint do not cover for all the antifouling application, for istance a certain cruising speed need to be reached, not suitable for static construction (i.e. fishfarming) low mechanical resistence and high cost (as well descrivbed in your article).
    We trust in the smart use of the biocide, keeping in mind the cost aspects (as Dr. Katy Wolf did), and hope for a future with at least less biocide accumulation in the marine biosphere.
    Sincerly Your
    //Emiliano Pinori

  2. Cyrus says:

    Emilio, Thank you for the comment and the links to your relevant work on antifouling paint. I have added your LEAF project to the list of additional resources.

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