Is Copper Bottom Paint Sinking?

Ryck Lydecker

More than two decades ago, the U.S. outlawed toxic tributyltin (TBT) in antifouling bottom paint, and copper-based substitutes took over to control marine growth on the hull.

Last year, Washington became the first state to ban copper paint on environmental grounds. Now the California legislature is taking up similar restrictions.

When it comes to painting the bottom of a recreational vessel's hull to discourage marine growth, boaters currently have a wide array of products from which to choose. And while the choices can be a bit bewildering, beginning January 1, 2020, boaters in the state of Washington can scratch off their lists any paints that contain more than 0.5 percent copper. That's because last year, in response to concerns about contamination in Washington waters, the state legislature outlawed copper-based antifouling paints. (Paints on the market today contain 20- to 70-percent copper.)

This ban applies only to private recreational boats 65-feet and under. That leaves commercial, government, research, and for-hire passenger vessels — not to mention large ocean-going ships that frequent Washington waters — free to discourage marine growth with paint that recreational boaters can't use. And the fine, if they do, is a maximum $10,000 per day.

Copper, the fouling control substance of choice for the past two centuries or so, first as sheet cladding for wooden ships in the days of "iron men" and in more recent times mixed in bottom coatings, could be headed the way of tributyltin (TBT). Two states away, the California Legislature came close to passing a similar copper-paint ban last year. The measure, now amended to allow use of low-leach-rate copper paints, is back for debate in Sacramento, and likely a vote, in this year's session. Discouraging aquatic critters from taking up residence on a boat's bottom and on its submerged running gear is what antifouling paints are designed to do. So let's look at the problem with copper as the key ingredient in those paints.

Getting To The Bottom

Whether it's animal fouling in the form of the old familiar barnacle, or a relative newcomer, the zebra mussel, or plant and slime growth, most antifouling paints work by dissipating metal at the hull's surface to kill organisms or prevent them from adhering. Since the demise around 1988 of the all-too-effective tin compounds that also proved highly poisonous to underwater ecosystems, not just to hull growth, copper became the biocide of choice. But the metal-biocide approach has a downside.

Photo of painting the bottom of a boat with copper paint

"Copper bottom paints actively leach into the surrounding water to deter growth; in other words, they do what they're supposed to do," says the Port of San Diego's Karen Holman. "The problem is that the chemical cuprous oxide released into the water column can reach high enough levels that it can become toxic to marine organisms, in the water and in the bottom sediments. Especially with the way marina basins are designed, to prevent a lot of wave action, they can have limited water circulation and low flushing rates. The build-up of copper in the water column is an unintended consequence of using antifouling paints and that can lead to toxic effects on larval development of some organisms."

Holman, who's the port's senior environmental specialist, is at the epicenter of the debate over how to address those consequences. The port's Shelter Island Yacht Basin is home to three major marinas, three yacht clubs, and some 2,300 recreational boats. There, water sampling in the 1990s revealed dissolved copper concentrations high enough to be deemed a threat to the ecosystem. While a relatively abundant natural element, even essential for human health in small quantities, copper is a metal that falls under U.S. Environmental Protection Agency (EPA) water-quality regulation. As a result, in 1996, Shelter Island made the state's list of "impaired waters" under the federal Clean Water Act. California has more than 1,100 water bodies on that list, with problems ranging from bacterial contamination to just plain trash. In San Diego Bay all of its boat basins are listed as impaired for copper.

"That put the regional water boards under pressure to fix the water-quality problems," reports Cleve Hardaker, vice commodore of Shelter Island's Silver Gate Yacht Club at the time. "In 2003, our regional water board picked Shelter Island as its water-quality-compliance target case. Studies determined that 93 percent of the copper came from passive leaching of bottom paint, with a further five percent attributed to in-water hull cleaning that was accelerating the release of copper. None of us were experts, but we didn't believe that the sources had been adequately assessed. We didn't have the funds to do our own research," explains Hardaker, now president of the Recreational Boaters of California (RBOC). Since that time, he notes, studies done elsewhere have attributed a much larger share of the copper in the water column to over-aggressive in-water bottom scrubbing, 45 percent in one case.

Table showing top painting in SanDiego Port Authority testsThe San Diego Port Authority tested 21 paints on submerged fiberglass panels. In subsequent field testing of the 11 top-performing products from the panel tests, when applied to boat hulls, only four products scored "good" under the project's rating criteria (see above).

The water board set an allowable Total Maximum Daily Load (TMDL) for copper, and required a reduction by 76 percent as of 2022. Identified "responsible parties" to the rule are the port, as landlord of Shelter Island, plus the marinas, yacht clubs, and individual boat owners there.

"The TMDL clock started ticking in 2005 and the port brought in the stakeholders to develop a plan to convince boaters not to use copper paint," Hardaker goes on. "But the problem was, we had really no alternatives readily available. If there were products that were effective and cost-comparable, then boaters would use them; we could educate the boaters." So the port set out to find alternative coatings and compare them to paints then in use at Shelter Island.

What's Fair Is Foul ...

"In general, I think boaters are very environmentally conscious; they do have a desire to protect water quality. But I also think they're cautious [when it comes to change] and I understand that," says Holman. "That uncertainty, or fear, has to do with not understanding the alternative products or how best to use them."

For that reason, the port undertook a three-year research study, funded by the EPA, to evaluate currently available low- or non-copper paints in terms of hull preparation and product application, performance (the ability to deter fouling and the amount of bottom cleaning required), and cost-effectiveness over the life of the paint job. With traditional copper paint as the baseline, testing included biocide and non-biocide products and used a two-phase approach. The nonprofit Institute for Research and Technical Assistance (IRTA), based in Los Angeles, worked with the port to conduct the testing in cooperation with a stakeholder group drawn from the boaters, several boatyards, and 23 paint manufacturers (including Pettit, Interlux, ePaint, and Sea Hawk).

The first phase tested 46 coatings applied to fiberglass panels that were immersed in San Diego Bay, followed with regular cleaning, over four months. That phase cut the field to 21 "top performing" coatings and, of those, 11 were applied to boat hulls and evaluated over 20 months (see chart). A summary of the study, published in January 2011, states: "Non-biocides, in particular the soft non-biocide coatings, were identified as the best alternative options tested."

With 2,300 boats in Shelter Island Yacht Basin, more than 1,700 boats would have to switch to non-copper bottom paint to meet the mandated 76-percent copper reduction by 2020, Holman says. To encourage the shift, last year the port embarked on a second project, with $600,000 from the California State Water Resources Control Board, to help offset the costs of removing the copper for boaters willing to make the switch. One of the chief considerations in the decision to switch to biocide-free non-copper coatings is the careful hull preparation required, which for most products necessitates stripping or sanding off the old paint. (Completely stripping a 30-foot boat in the San Diego area can cost $2,500 or more, according to IRTA.) To be on track to meet the 2020 deadline, an estimated 10 percent of boats should've switched over by the end of this year, Holman says. But boaters aren't exactly lining up to convert. Indeed, Hardaker said at the end of November, he was aware of only two.

Bottom-Paint Blues

The "voluntary" aspect of conversion could become moot (even by the time you read this) if a bill now before the California Legislature is enacted. Introduced last year, it sets a January 1, 2015, deadline for copper-containing paints to meet low-leach rates as determined by the California Dept. of Pesticide Regulation [CONFIRM]. So if California goes the way of Washington, is it a matter of time before boaters across the country are faced with a copper conundrum in their own states?

"I was very involved in the TBT regulations in 1988, so I've been down this road before," reports John Ludgate, now president of Pettit Paints but then with Interlux. "This time, even though Washington and California have taken actions to restrict it, I don't see copper legislation rolling toward the Eastern Seaboard. As paint companies, we're not panicking because we have [non-copper] products already and obviously the technology will get better. Right now every paint company has at least one product without copper, and over time we'll all develop the 'good, better, best' products for non-copper bottom paint."

But that market is small, Ludgate adds, only about one-percent of the industry's sales because the products are fairly new and may only appeal to "early adopters and boaters who are especially sensitive to environmental issues." The most usable replacement these days, according to Ludgate and others in the industry, is Econea, a pharmaceutical product that has a very rapid half-life, meaning it disappears quickly in the water. One of the challenges with copper, he notes, is that it doesn't break down quickly. He adds that "some of the copper manufacturers would argue that it breaks down from its toxic form to an inert form in a matter of days." But Econea, as a biocide, needs a "booster" in the form of zinc (usually two percent) and some experts in the boating industry fear that zinc, too, could eventually raise environmental concerns.

Table of 40-foot Sailboat Paint Cost ComparisonThis table shows annualized costs of prepping and painting a 40-foot boat, amortized over te life of copper paints, or one of three different kinds of biocide-free paints. Paint life projections are manufacturers' estimates. The comparison assumes a cleaning every three weeks.

"There is no real substitute for zinc because you're not going to get antifouling paints that work well enough without it," reports Elenor Ekman, marketing manager for Interlux, which claims to be the first manufacturer to enter the recreational market with a copper-free antifouling paint, using Econea as a biocide. Registering a new biocide in the U.S. is extremely difficult, Ekman says, and can take years because these compounds are regulated as pesticides. The EPA must conduct various toxicity studies and confirm the results to approve a new product. Each state also regulates antifouling paints as pesticides, adding another challenge in bringing new products to market. Indeed, California's Department of Pesticide Regulation only approved a metal-free Sea Hawk paint for use in the state last November after the company submitted its product to more than two years of evaluation in addition to the federal EPA requirements.

In the case of the Interlux Econea formulation, the EPA approved it for the recreational marine market in 2009, after five years under review. "Econea deters the hard-shell fouling," Ekman explains. "Barnacles in particular don't like the material and don't tend to stick." The product also uses zinc omadine as an added biocide to deter soft-fouling organisms such as slime, algae, and weed. While zinc is certainly a metal that falls under EPA regulation, it's also used in small quantities in dandruff shampoo, children's face paint, and in another very important bottom coating, diaper-rash cream.

Is There A Different Way?

"I think the future is in non-biocide paints," says IRTA's Dr. Katy Wolf, who conducted the testing for the Port of San Diego. "Here's what everyone did: They went to TBT and that got banned worldwide so they moved on to copper, and now copper is causing problems. The inclination is to move to the next biocide but that's just going to cause problems down the line. So I think you have to move directly to the non-biocides, but those are more expensive. First, the coatings themselves cost more than the copper paint. Most require that the hull be stripped before application to provide a proper substrate for bonding, and this is the highest cost component," she adds. "The third factor is that many non-biocide paints must be sprayed on, not applied by roller, and that's more expensive, maybe $600."

Having completed the San Diego project, Wolf has embarked on a new one, with EPA funding, to make it cheaper and less complex to apply the non-biocide paints, and thus reduce the overall cost of using them. She's also exploring coatings that can encapsulate copper paint and thus avoid expensive hull stripping altogether. And where stripping or sanding off copper paint is still required, she's developing a recycling market for the dust, now disposed of as hazardous waste. That saving to the boatyard, which she estimates at about $2,000 for a 30-foot boat, could be passed on to the boat owner. (See accompanying table.)

Independent Field Testing

But are today's non-biocides, typically called "foul release" coatings, effective on marine growth? "In the San Diego project, we did a ton of work with these paints," Wolf continues. "It turns out with the soft non-biocides based on silicon, you can clean them fairly readily with gentle methods on the same schedule that you would clean copper. So you have the same maintenance costs, ultimately."

That may be the case in Southern California waters, but in the broader market where regular bottom cleaning is not the norm, the average recreational boater won't accept the added maintenance that the soft non-biocides require, according to Pettit's Ludgate: "The softness of the coating is what makes it effective in keeping barnacles from attaching. Conversely, from a practical stand-point, if you hit anything, it kind of rips easily." He also notes that the hard, slick, non-biocide paints tested in San Diego are particularly effective on commercial vessels that spend far more hours underway, and often at higher speeds, than the average recreational boat, thus washing off growth.

For more than a decade, the boating consumer-reporting publication Practical Sailor has measured the effectiveness of all types of antifouling paints and other bottom coatings from most of the major manufacturers through testing in both Long Island Sound and southwest Florida waters. Editor Darrell Nicholson, who's in charge of the testing, has monitored this evolving technology and its rapid development as the new market for these paints has driven increased research and development. The good news, according to Nicholson, is that a couple of the zinc-Econea paints have gotten top scores in the Practical Sailor long-term tests — an excellent sign for the future of these paints. Yet, he says, "there have been a couple of flops over the last five years or so, too." His concern is the complexity and added expense of the application process. "Some paints may require three coats and the coverage ratio is much less than with copper." His advice is to be wary of any new paint unless it's been on the market for at least a couple of years, and has a solid track record of high performance.

The subscription-only monthly publication tests about 60 bottom paints that are marketed to boaters every year. Nicholson says his testing has shown that many of the non-copper, non-biocide products have shown deteriorating results after 18 months, some even earning "Poor" ratings as hard growth is detected on test panels. But, he notes, developing copper-free, biocide-free paints is "an evolving technology" within the coatings industry. "Copper is a commodity and it's getting very expensive," says Nicholson. "So the manufacturer who can make an effective eco paint without it, and without any other biocide, will lower their costs tremendously. It's the Holy Grail for paint manufacturers."

For a full discussion of bottom paints (formulations, uses, application, and maintenance of various products), visit the West Marine Advisor at: and look for the "Antifouling Paint" article posted there. Or, to request a copy via email, contact: 

— Published: February/March 2012

The Practical Side Of The San Diego Study

After the San Diego Unified Port District released findings of its study on alternatives to copper bottom paint, the consumer-reporting publication Practical Sailor offered readers its own perspective on the report. Here are highlights from that story, published in March 2011.

San Diego port officials forwarded their "Final Report on Safer Alternatives to Copper Alternatives to Antifouling Paints for Marine Vessels," to the EPA in February 2010. Presenting data on a wide range of alternative antifouling paints that contain limited or no harmful biocides, the 152-page report is based on both controlled panel tests and field tests on several different powerboats and sailboats that berth in the port district. In the preliminary panel test, several mainstream paints that used a zinc biocide were effective, but because the goal of the test was to find alternatives to biocides, very few zinc paints went on to the second round of field tests on boats.

The report includes an economic analysis of the annualized cost of using a paint that has no biocides. According to the study, once the application and cleaning costs are amortized over the life of the paint, the costs of using a hard, slick, non-biocide paint are comparable to the annual expenses for using copper-based paints. (Panels were cleaned every three weeks for the test.) However, the most optimistic cost estimates for non-biocide paints rely on a five- to 10-year projected life span for hard, slick, non-biocide paints. The San Diego in-the-water hull tests lasted fewer than two years, so the longer projections were based on manufacturer-supplied data from large commercial ships, the primary users of these types of paints. Nevertheless, the study's authors suggest that such lifespan projections are not unreasonable, as long as boat owners adhere to the recommended maintenance regimen. The report concludes that the successful transition to a non-biocide paint will require close cooperation of regulators, boat owners, paint manufacturers, boatyards, and hull cleaners.



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