Coppercoat theory – how does it actually WORK?

[Sportswagoneer]

So after having coppercoated my 40 foot Hanse two years ago with a little mixed experience - I’ve been reading up heavily and want to try to sum up my understanding of how coppercoat actually works. I realize there’s been tons of posts before (and I’ve read most of them). It’s also clear that real-life performance varies greatly. Still no one really puts it all together from the theoretical side (rather than application, treatment etc.) Being a nerd at heart, I need to understand the workings of something in order to be able to work with it properly.
Comments are welcomed off course - but please try to be specific? Where exactly am I wrong (or correct) in my understanding? And please stick to the topic? Pretty please?

Here goes:
Coppercoat inhibits fouling in two ways: By exposing copper to seawater for oxidation, thus releasing biocides AND by producing a smooth, slippery surface that’s difficult for marine growth to hang on too. I believe BOTH these requirements must be met in order to achieve the “success story efficacy” that some are boasting.

• Copper as a biocide:
  • The special epoxy allows for a very limited degradation/leeching, producing a minor copper exposure and oxidation even without abrading the surface. This will only suffice if the surface is smooth AND fouling conditions are low or moderate.
  • By sanding/burnishing the surface lightly, more copper is exposed. This is sufficient for many happy customers.
  • However: With a less than smooth surface and/or in heavy fouling conditions, the amount of copper leeched through the epoxy will just not be enough compared to traditional copper-based anti-fouling paints.
• The slippery surface:
  • People with successful applications talk about a slippery, smooth surface. In particular, the Sailing Britican folks comment on this difference after their final and successful application.
  • Marine growth loves tiny cracks, scratches etc. to find foothold for colonization. Since the CC releases Copper biocides at a very low rate (accounting for the long durability), a less than smooth surface will be enough to tip the scales in favor of fouling in high growth conditions.
  • A less than perfect application will produce a more uneven surface before sanding.
  • Sanding with rougher than 320grit paper produces tiny scratches and may end up increasing the ease of colonization rather than decreasing it.
  • Sanding an entire hull down from “rough” to “smooth” with 320grit paper is virtually undoable, requiring hundreds of work-hours with a random orbital sander. Thus - a good base application seems to be a requirement for a good end result.
  • A certain “orange peel” surface is common, making it hard to sand sufficiently to expose copper even in the “bottoms”.
  • In “Sailing Britican’s final application video” they use epoxy only (no copper) in the first layer. This may be a good trick to secure a smooth surface.

Thanks for reading all the way through! Please do point out exactly where I may be at fault in my understanding?

[tkeithlu]

Welcome to the forum, Sportswagoneer.

Nice summary. I usually rely on my chemist admiral for understanding of such topics, but cannot fault your reasoning. I can confirm the "hard substrate" situation for barnacles; their entire life depends on finding something hard to adhere to, and they've evolved some pretty good tricks for success. I suppose I could go as far as to say that I've never seen a hull surface so slick that they couldn't grab hold in the thousands.

So what now? You say that you got mixed results, and there's an implication that you are in a fairly nasty location for barnacle growth. It also appears that making a smooth enough surface to minimize adhesion was a challenge. It sounds like time to switch to a bottom paint that will work under your conditions.

[sailorboy1]

I think a lot of bottom paints fail due the”slippery surface”. Boats that sit around start to collect dirt on the hull and then growth gets a foothold on that, which in turn leads to more dirt/growth.

But of course that doesn't address why hard growth attaches to a nice clean freshly bottom painted hull like it did in the first month for more expensive crappy Seahawk painted bottom.