TL;DR
"The paint below the waterline is red because it contains copper, which increases resistance to fouling, the build-up of biological matter such as barnacles, seaworms, and algae."
TL;DR
"The paint below the waterline is red because it contains copper, which increases resistance to fouling, the build-up of biological matter such as barnacles, seaworms, and algae."
Here is a for anti-fouling hull paint. There is only so much one can do to meet the requirements. The first coat is nomally a red oxide anit-rust prime coat, applied at over five mils dry. The second coat is another anti-rust paint, but it's specified to be gray. The anti-fouling paint needs 3% copper in it. The best way to hide the copper and meet the other requirements is to make it red(ish).
Here is a [MIL spec](http://paintsdopesvarnishesrelatedprodu.emilspec.com/MIL-PRF-24647/page10.html) for anti-fouling hull paint. There is only so much one can do to meet the requirements. The first coat is nomally a red oxide anit-rust prime coat, applied at over five mils dry. The second coat is another anti-rust paint, but it's specified to be gray. The anti-fouling paint needs 3% copper in it. The best way to hide the copper and meet the other requirements is to make it red(ish).
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