ANTI-FOULING FILES: 2. Copper-Free Paint Options

Tanton 39 out of the water in white paint

Having blasted the bejesus out of the nether regions of poor Lunacy’s hull (see our last episode), I next needed to decide what anti-fouling paint to dress her up in to make her respectable again. In the Good Old Days we never worried about such things. When I was a boy, so much poison was being pumped into the Kennebec River we didn’t have to put any poison paint on our hulls to keep them free of marine growth.

Such are the joys of ignorance. These days, of course, governments are very sensitive about inflicting toxic substances on the environment. This has complicated anti-fouling paint selection, especially for folks like me who have boats with aluminum hulls.

Currently, the active ingredient in most garden-variety anti-fouling paints is cuprous oxide, which reacts galvanically with aluminum and so corrodes aluminum hulls it comes in contact with. (Bummer!) Before we cared about the environment, it was possible to use tin-based paints, which are both extremely effective and are compatible with aluminum. (Yay!) Now (unfortunately or not) these paints are illegal in the United States and much of the world. These days most bottom paints billed as being safe on aluminum in fact contain copper thiocyanate, a less reactive form of copper that can still cause damage if not separated from an aluminum surface by an effective barrier coat.

I was determined to use a copper-free paint on Lunacy, as I really don’t want to worry all the time about whether her barrier coat is perfectly intact. (Grounding on rocks, for example, is awful enough without having to fret over whether your hull will be chewed up by corrosion because your paint job has been breached as a result.) There is already a small selection of such substances available, and it seems likely to me that the future of anti-fouling paint lies in this direction. Like tin-based paint before it, poisonous copper-based anti-fouling paint is the focus of increasing regulatory scrutiny and will probably be banned eventually in both the U.S. and Europe.

My research on the subject brought me eventually to E-Paint. This is an ablative photo-reactive zinc-based anti-fouling paint (the active ingredient is zinc omadine) that is non-toxic and cannot harm either the environment or aluminum. I had heard some reports of adhesion problems with E-Paint. Joe Sharpe, who blasted my boat, was among those who recommended against it for this reason. But one friend of mine who actively cruises an aluminum boat on both sides of the Atlantic reported he has had good results with it. I was encouraged, too, by the fact that the U.S. Coast Guard uses it on all its aluminum vessels.

The folks at E-Paint were certainly very helpful. Mike Goodwin, an E-Paint technical guru, made a special trip from Falmouth, Massachusetts, where the company is based, up to Portland Yacht Services just to inspect three profile samples that Joe Sharpe blasted on Lunacy‘s bottom. After examining the profiles with a magnifying glass and a special micrometer, he made a selection and recommended an application schedule: 3 coats of EP Primer (an epoxy-based barrier coating), 1 flag coat of grey hard paint (EP-ZO HP), following by a surface coat of white ablative paint (EP-ZO), with an extra coat at the waterline.  White was not an aesthetic preference, but a prosaic one, as this color E-Paint is reportedly most effective in combating bio-fouling on hulls. The extra coat at the waterline is recommended because this is where the paint is exposed to the most sunlight and wears away fastest.

Inspecting sponge blast profile
Mike Goodwin (without flashlight, above) inspects blast profiles on Lunacy
Measuring sponge blast profile
First he takes an impression of the profile with a piece of tape
Micrometer for measuring sponge blast profile
Then he measures the profile with a special micrometer

In my first full year using E-Paint on the boat–with a summer season spent in Maine and a winter season spent in the Caribbean–I found it to be reasonably effective, though not as effective as poisonous copper-based paints. It seemed very effective at the waterline, but wore away quickly there, in spite of the extra coat there. On deeper parts of the hull it did a mediocre job combating slime and a good job, I thought, of resisting hard growth. During the course of that year Lunacy‘s hull was scrubbed three times–twice in a very cursory manner by me in a snorkel and mask and once quite thoroughly by a diver in scuba gear. What little hard growth did appear was easily knocked off with a scraper.

Adhesion was much more problematic. On hauling the boat again in Portland after returning from the Caribbean (see the photo all the way up top), I found there were a few discrete areas where patches of paint had fallen off. Apparently it was the flag coat of hard paint that had let go of the barrier primer beneath it. These areas were relatively small (just 2 to 3 inches in diameter) and were not very numerous.

But after the boat was out of water for over a week there appeared much larger areas where the paint seemingly dried out and then flaked off in tiny fragments when disturbed. I consulted with Mike Goodwin, and he advised this is typical in areas where the paint has grown thin and is exposed to sunlight out of the water. He suggested this effect should be most pronounced on the side of the boat most exposed to the sun, which was in fact the case.

Poor bottom paint adhesion
The E-Paint started flaking off Lunacy’s keel after she was a week out of the water

Mike recommended sanding the affected areas with 80-grit prior to recoating the entire bottom with more white EP-ZO. I did this (I put on two coats this time, plus a third at the waterline), then relaunched the boat for another summer in Maine and winter in the Caribbean. But by the time Lunacy got south in November, her bottom paint was again already looking pretty tatty. Rather large areas had flaked off in the water, and as the winter progressed it seemed the paint was less effective than before. Though hard growth never became a real problem, there was lots and lots of soft growth. Each time we went down to St. Martin to use the boat I had to hire a diver the scrub the bottom hard, and by the time I sailed it back to Maine much of the paint was gone (due both to the scrubbing and continued flaking).

For Lunacy’s most recent haul-out at Maine Yacht Center, I was therefore determined to try another paint. But if I wanted to stick with copper-free paint, I found there was really only two other options: Interlux’s new Pacifica Plus paint (which contains the proprietary biocides Econea and Biolux) and Pettit’s Vivid Free (which, like E-Paint, is zinc-based, but is not photo-reactive). In the end I elected to give Vivid Free a try, primarily because applying it involved less prep work. Interlux’s tech people recommended both sanding off the old paint and laying down a new primer, where Pettit recommended only a thorough sanding with 80 grit. Also, though Vivid Free is an ablative paint, it evidently is not so soft that it wears away quickly.

In discussing all this with the guys at MYC, their feeling was that the awful adhesion problem I’d had with E-Paint was not inherent to the paint itself. They urged instead it was because the paint had been “hot-coated” over the primer. That is, instead of sanding the barrier primer, the finish coats had been applied within certain time and temperature windows so as to create a chemical bond between layers. Though we had followed E-Paint’s hot-coating instructions to the letter when painting Lunacy last time, it seems we ultimately failed to achieve a good chemical bond between the layers of primer and paint. In cases where E-Paint is applied after sanding, so said the MYC crew, adhesion (in their experience) has not been a problem.

So I haven’t yet written off E-Paint as an anti-fouling option. For one thing, they offer the only hard copper-free paint, and there are some advantages to this, particularly if you favor performance. But right now I’m digging Lunacy’s new black Vivid Free bottom.

Boat in Travelift slings
Lunacy in her new coat of Vivid Free, ready to swim again

I think it looks much better than white! (Meanwhile, of course, I’m also keeping my fingers double and triple crossed that it will actually help keep gook off my hull.)

Next Episode: My Ace-in-the-Hole (Maybe)

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5 Responses
  1. Rob Hoffman

    Hi, Charlie…
    We sail an Alubat OVNI Sonate 28 of 1983 vintage and have used epaint ZO on her with good results, but we did not use the primer…just sanded the old off and applied ZO as per instructed. Adhesion has not been a problem and the boat has had two seasons of use so far and the paint still is intact and clean…but in fresh water use only. I’m going to ZO-HP next time around as this boat is trailer based and HP is better suited to that use. We dearly love our aluminum lady and the epaint has performed well for us so far.

    Thanks for a fine blog! Rob Hoffman S/V “CanCan”

  2. Al Egenriether

    Hi. I saw your boat this summer in the North Channel and wanted some information on it but didn’t get a chance to talk to you. Your boat is the most impressive thing I have ever seen on a trailer. We were the guys with the little green Potter 19 that ended up side by side at customs when returning to the US. Do you have a website with info on your boat or something? Thanks for your time. Al

  3. Charlie

    Response to Al below: I think you’ve got the wrong guy. I hear it’s great, but I’ve never sailed the North Channel. And I’ve never had Lunacy on a trailer that traveled more than a few yards. I’ve always admired the Potter, however! Thanks for stopping by. Charlie


    Hi, Just read your article 2 – Copper-free bottom paint. We are on an aluminum trawler, and have struggled for years finding a good solution. We were wondering if you have an update on that article, which I believe was from 2010. Thank you.

    1. Charles Doane

      Hello Donna! I must confess, I finally gave up on “eco” type soft copper-free ablative bottom paints. None of them were that effective, particularly in the tropics, and in the end I always needed to give my bottom a good scrub from time to time to keep it clean. And every time you do that with a soft paint, you end up losing a good deal of paint. Kind of aggravating, given how expensive the paint is! So… now I’m using Trilux, which has copper thiocyanate in it, a less reactive formulation, but still, as noted in the post you cite, you need a good barrier coat between it and the hull. It is also a harder paint, so you can scrub it without losing too much of it. It works well enough, but now I have to be careful to promptly repair any breaches in the barrier coat.

      I’ve often daydreamed about coating my bottom with some highly effective tin paint someplace where it is legal… the Bahamas, say, or the BVI. But one friend who recently did this told me they regretted it, as the tin paint is not compatible with most other paints, and they had to strip their bottom and start all over again when it was time to repaint in the US.

      I hope this is helpful!

      cheers, charlie

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