Copper content of bottom paint

Don S/V ILLusion · Mar 23, 2013

The copper content can be misleading and isn't a good indicator of efficacy. Don't believe the advertising. The best advice you can get will be from folks in your specific area in terms of what works best for the water there.

Just keep in mind the tendency people have in thinking their choice is the best. Ask around and get a consensus or better yet, find someone you know to be objective and ask him/her.

What works in my area may not in yours.

Johnnie Walker Black · Mar 23, 2013

Uh... I'm sorry but copper content is the single biggest indicator of efficacy of a bottom paint.
Copper is in most cases the biocide in the paint that prevents growth. More copper= less growth. Yes there are some other factors ie. the biocide delivery mechanism or chemistry of the paint that can effect the paints effectiveness to some degree: but that being said, copper is the active ingredient here.

Don S/V ILLusion · Mar 23, 2013

Johnnie Walker Black said:
Uh... I'm sorry but copper content is the single biggest indicator of efficacy of a bottom paint.
Copper is in most cases the biocide in the paint that prevents growth. More copper= less growth. Yes there are some other factors ie. the biocide delivery mechanism or chemistry of the paint that can effect the paints effectiveness to some degree: but that being said, copper is the active ingredient here.

It's the available copper that determines it's efficacy, not the copper by weight figure. There is a world of difference.

Exaggeration for effect - consider a copper plate which has been sealed with an impervious coating. The copper content by weight would be(misleadingly) high but it's usefulness as a biocide would be negligible.

The mfgs don't denote active copper, just the weight.

fstbttms · Mar 23, 2013

Johnnie Walker Black said:
Uh... I'm sorry but copper content is the single biggest indicator of efficacy of a bottom paint.
Copper is in most cases the biocide in the paint that prevents growth. More copper= less growth. Yes there are some other factors ie. the biocide delivery mechanism or chemistry of the paint that can effect the paints effectiveness to some degree: but that being said, copper is the active ingredient here.

+1

The best thing ever posted on this forum about bottom paint that wasn't written by me.

fstbttms · Mar 23, 2013

Don S/V ILLusion said:
It's the available copper that determines it's efficacy, not the copper by weight figure. There is a world of difference.

No there isn't. All of the copper in anti fouling paint is "available" for retarding fouling growth. A paint that is 60% copper by weight isn't holding back 10% or 20% of that copper for some mysterious reason. Every ounce of that 60% will leach out of the paint, given enough time.

Gunni · Mar 23, 2013

howdy neighbor! Pettit Hydrocoat works well around here, and is 40% copper. I'm switching to Hydrocoat SR this season to gain more biocide for our summer soft growth. Water-based Hydrocoat is as easy to apply as flat wall paint. And easy cleanup. I like to thin it a little to manage build up season to season. And it stays active during winter layup.

RichH · Mar 23, 2013

Local bottom paint knowledge for the Upper Ches.:

Bottom paint on the Upper Chesapeake, which varies at times between fresh to salty (brackish) and depending on the direction of the prevailing winds, how polluted the water and how 'extremely turbid' the water is ... is usually a crap shoot. Plus, the Upper Chesapeake is in the beginning stages of Zebra Mussel invasion.
By crap I mean literally and figuratively.

Mahogany Tides (explosive growth of toxic microorganisms) will surely cause SLIME accumulation on a hull and the slime will allow 'hard growth' (Barnacles, etc) to get a good 'foothold', even on high copper content paints as the slime will 'seal off' the copper action.

Other factors include the water flow or stagnation characteristics of exactly where you moor or slip your boat.

For the past few years, especially on Worton Creek, bottom paints with Biocides to prevent/retard slime growth have worked the best. Example: Interlux "Ultra", etc. .... But should be applied 'as smooth as possible' so that the slimes, etc. more easily 'release' when the boat gets up to hull speed, or you can simply occasionally 'wipe' the hull with a simple plastic/polymer 'squeegee' or very soft brush mounted to a long retractable painters extension pole.
For the 'easiest' way to get a relatively smooth hull with ablatives, is to 'thin out' the paint to the maximum specified dilution and use a THIN foam roller to apply on a relatively WARM day. The yellow WEST SYSTEM epoxy rollers are probably the best to use but the foam will eventually break loose due to the solvent/thinner ... so youll probably need at least 3-4 foam WEST SYSTEM rollers if you work fast and before the thinner/solvent ruins/dissolves the foam roller.
Consider to use a barnacle barrier on your prop and shaft: Petit Zinc Rich Barnacle Barrier spray paint.
The problem with most water based paints is that you cant get them 'smooth enough' as you can with solvent based ... and you dont want 'rough' when massive slime is the prevalent problem.

As you already experienced, with toxic 'mahogany' tides causing great amounts of slime and its accompanying great barnacle attachment, the debris falling off a hull when scrubbing is extremely toxic and can cause violent reactions to human skin, mouth parts and to human respiratory tissue. So, anything you can do to help to keep the toxic slime off will be of benefit.
You're a nice guy; but, I really dont want to consider doing "mouth to mouth" on you, ... like last time. ;-)

Don S/V ILLusion · Mar 23, 2013

fstbttms said:
No there isn't. All of the copper in anti fouling paint is "available" for retarding fouling growth. A paint that is 60% copper by weight isn't holding back 10% or 20% of that copper for some mysterious reason. Every ounce of that 60% will leach out of the paint, given enough time.

That is flat wrong. i know you clean boats but that doesnt equate to a fundamental understanding of the chemistry involved. Unless you can cite specific leachability data demonstrating such a statement, it only serves to mislead.

Without going into the chemistry, imagine common table salt. It is composed of chlorine and sodium. Using either as the metaphor for copper, imagine if either the Na or Cl was available in a dissociated state. You would have a toxic cloud in a highly exothermic reaction. The same principle which binds the Na and Cl also serves to bind copper causing some portion to be inert.

If you want a more detailed explanation as it relates directly to bottom paint, I could recommend a number of books.

Paul Mermelstein · Mar 23, 2013

I am a bit south of you and sail the entire bay. I have had excellent result with Trinidad SR from Pettit. It's not an ablative , but a "hard" epoxy. It lasts at least two seasons, goes on easily, and it can be wiped down by a diver a couple times a season without leaching into the water. Only down side is that after about ten years, the five coats that have built up need to be sanded off.

fstbttms · Mar 23, 2013

Don S/V ILLusion said:
That is flat wrong. i know you clean boats but that doesnt equate to a fundamental understanding of the chemistry involved. Unless you can cite specific leachability data demonstrating such a statement, it only serves to mislead.

Here is a good read from Interlux Paints regarding the formulation of anti fouling coatings and how they work. Much is said about the various forms of copper used in anti fouling paints and how that copper is delivered to the surface of the coating. I can find no reference indicating that some percentage of the copper in the paint is not available to retard fouling. However there are many references about how much copper leaches out and in fact one statement that specifically says, "too thin a film will lead to rapid failure once all the biocide has gone."

http://www.yachtpaint.com/LiteratureCentre/antifouling_101_usa_eng.pdf

So I don't know if you are correct or not. Maybe you could provide some documentation supporting your position.

centerline · Mar 24, 2013

fstbttms said:
Please provide proof that your position is correct and mine is not. Without it, your claim is no more valid than mine.

after reading both disagreeing posts, to someone like myself who doenst know how the process really works, but just trusts that it does, would make us believe that the best thing to do if we want the ultimate in bottom protection, is go to the store and buy the highest content copper paint on the shelf, no matter if its made by dutch boy or the acme epoxy company.....

but my thought process tells me that the epoxy filled with copper would be a useless barrier due to the epoxy sealing in the copper and not letting it be available to the enviroment.... but as you say, given enough time, it will all leach out and do its work, I would think if it leaches out too slowly it would be ineffective in its job anyway......

but if the copper was in a binding agent that was too quick to release the copper, it would be super effective for a very, very short amount of time... and dump the copper from the boat to the environment without its useful, purposeful life being fully realized as a marine growth inhibitor on the bottom of a boat

so with all this over imaginative thinking, it would lead one to have the idea that the copper content has to be balanced with the proper "time release" agent so that it ablates and releases the proper effective amount of copper during the life of the paint..
so more copper content wouldnt necessarily be the most important factor, but the available, exposed copper during the life expectancy of the paint would be..... but I am not implying im right, but thats just my conclusion of how it should work....

fstbttms · Mar 24, 2013

Don S/V ILLusion said:
The same principle which binds the Na and Cl also serves to bind copper causing some portion to be inert.

From the same web site I linked above- a sample anti fouling paint can ingredient lable:

Note that Cuprous Oxide is listed as 38.62% by weight, co-biocides are 2% and inert ingredients are 59.38%. Is it your contention that some of that active copper is actually an inert ingredient? Wait- that couldn't be right because then the numbers wouldn't add up to 100%! Maybe the inert ingredients include some Cuprous Oxide not listed in the 38.62%. But if that were the case, the 38.62% active copper would all be available to retard fouling growth.

But hey, you're the scientist here. I'm just a hull cleaner with no grasp of how the chemistry works. Maybe you can straighten this out?

fstbttms · Mar 24, 2013

centerline said:
so more copper content wouldnt necessarily be the most important factor, but the available, exposed copper during the life expectancy of the paint would be..... but I am not implying im right, but thats just my conclusion of how it should work....

If you haven't already, you should read the document I linked to. Very informative and touches on all of the points you noted above.

Copper content may not be the only determining factor in the efficacy of an anti fouling paint but take my word for it; it is absolutely the most important one. Paints with high copper content (say 60% and above) are generally more far effective than those with low copper content. And that is regardless of the delivery method- hard, ablative or otherwise. If you keep your boat in a region of low fouling, you may not need a high-copper paint. But if you keep your boat in a high-fouling region (like California), I garauntee you'll find that low copper paints foul faster, require more cleaning and do not last as long as their high-copper counterparts.

The paint manufacturers aren't putting products on the shelves that leach too fast or too slow. They've spent decades and many tens of millions of dollars figuring out how to make the stuff work properly. But they are putting products on the shelves that may not be particularly suitable for the fouling conditions where you do your boating.

Calif. Ted · Mar 24, 2013

Many decades ago my organic chemistry professor in a lecture on "non-polar" solvents said "Water is the universal solvent, if you soak anything in water long enough it will dissolve, this includes stone and boats".

It's always been beneficial if not ecological here to pay for the highest copper content, with care it lasts 3 or 4 years in the water.

Johnnie Walker Black · Mar 24, 2013

Hey Don,

I for one would love to read the "book" you recommend on how available copper relates to anti fouling bottom paint.
Your assertion that copper content is not the primary factor In a bottom paints efficacy is absurd. And your retort that we should do more research before we comment is great advice that you should heed yourself. All bottom paints formulated with coppers are using cuprous oxide or cuprous thiocyanate: either of which...when allowed to leach or surface via the paint chemistry will be 100% available for anti fouling. Please get a clue, and stop passing bad information to other members of this forum with such an air of authority when you don't know what your talking about.

Don S/V ILLusion · Mar 24, 2013

Please rest assured I don't make unsupportable statements.

In this case, there are specific analytical procedures (reference below) which were used by the manufacturers required for submittal and certification of their products for sale in the US.
Although not the "book" I was referring to (any analytical chemistry text will do), copper bottom paint was and continues to undergo toxicity and efficacy testing for product development purposes necessitating continual data submission and review and none of the data correlates copper content to either toxicity (a determining factor in efficacy) or prevention of growth.

This is their data; not some testing done by the government.

Buying bottom paint based on copper content is analogous to buying a battery which weighs the most. People do that too but don't insinuate I don't "know what I'm talking about" just because you don't want to believe me.

I was trying to help as do many people here. With responses such as yours, many people might stop bothering.

www.epa.gov/osw/hazard/testmethods/sw846/pdfs/1313.pdf

Rick D · Mar 24, 2013

Come on guys, maybe there is just a chance an environmental and chemical engineer retired from the EPA might just know what he's talking about?

I don't think Don would disagree that everything else being equal higher copper is more effective. I think he's just saying everything isn't always equal.

wufibugs · Mar 24, 2013

Rick, I don't think that is the nature of the disagreement between Don and JWB. As I understand it JWB argues that, ultimately, all the copper in a copper based paint is available as an active biocide. If true, more copper means more efficient paint. Don argues that the chemical formulation of bottom paints is more complex, and more copper in the paint may not necessarily mean more copper in the water actively fighting slime. It is certainly an interesting point of contention and one that obviously has real merit for this forum given the number and regularity of threads on bottom paints.

It may well take a paint chemist to explain and resolve this very interesting, though unnecessarily heated, debate. PS rates Blue Marine's SCX at the top of the heap, and it happens to have the highest copper content. However, that does not by any means resolve the issue since the durability of the product can still be due either to the sheer volume of copper, or the genius of the paint formulation.