Can Copper Antifouling Paint be Kind?

By Darrell Nicholson, Practical Sailor

As we point out in the October 2012 of Practical Sailor, cuprous oxide (copper) still rules the roost when it comes to long-term antifouling protection, with hard paints and ablative paints fairly evenly matched for durability. For those who care about reducing their impact on the ocean, this raises a question: If we want to stick with copper (as opposed to an eco-friendly, copper-free antifouling), which type of paint – hard or ablative – is easier on the environment?

Copper leaching is the main concern among environmentalists, so it would seem a simple matter to discern which paints have the most copper in them. However, when comparing copper paints, it is important to note that the copper percentages listed on the can are usually calculated by weight. Which means that a paint that has heavier solids and resin may actually have more copper than a “thinner” paint that boasts a higher copper percentage. While some low-copper freshwater antifouling paints clearly have less copper than saltwater blends boasting 65-percent copper, there may only be a small difference in the amount of cuprous oxide in a paint that advertises 39-percent copper versus one that shows 45 percent.

To see whether we could nail down a more definitive answer this question, we turned to Interlux’s Jim Seidel (who, as far as I can tell, talks about bottom paint in his sleep). While he wasn’t able to provide a simple, clear-cut answer to our question, Seidel did provide some extremely useful insight into the way bottom paints work, which will help you make an informed decision when choosing a bottom paint-whether or not eco-friendliness is your top concern. — Read on.