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BoatUS Special Report

 

Is Copper Bottom Paint Sinking?

By Ryck Lydecker
Published: February/March 2012

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.)

Photo of copper-bottom of a boat

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 [CHECK], 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.

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