Topic: The big antifouling test 2023: The full results of our 18-month showdown (Read 32 times)
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Topic: The big antifouling test 2023: The full results of our 18-month showdown (Read 32 times)
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Most conventional antifouling paints use copper co*pounds suspended in a paint matrix that gradually erodes as water passes the hull, releasing the biocide at controlled rates, depending upon whether it’s a hard or soft-eroding type.
Coppercoat is an exception to the rule, because although it counts as a biocide, it uses pure copper particles set in a much harder epoxy resin that gives it a lifespan of ten years and greatly reduces the amount of copper released into the water.
Silicone-based foul-release coatings are another promising alternative, preventing fouling growth through the physical properties of its super-smooth hydrophilic surface.
BEFORE: As Raymariner looked when she was launched in June 2021
We wanted to find out if these alternative coatings perform as well as their traditional counterparts and whether their higher initial cost and fiddly multi-coat application regimes balance out with easier, more affordable annual treatments over time due to their longer lifespans.
Since silicone-based coatings work better on regularly used boats, Raymarine kindly allowed us to use their Hardy 42, Raymariner, as our test boat – although we did paint a static panel too to see how that fared.
Last year’s hot and wet weather may well have contributed to the excessive build-up of slime that greeted us when the boat was lifted in January. As you can see from the pictures, slime coated nearly all of our eight test strips, especially near the waterline.
AFTER – As she looked when she was lifted towards the end of January 2022
However, almost none of them showed any weed or barnacle growth, whereas the uncoated strips we left between some of the products were heavily fouled.
You can see a full table of costs at the foot of the page, but for the individual reviews we have quoted two prices. The first is our estimated price of the initial application to a typical 36ft boat, including any essential preparation costs such as stripping and priming (but not labour or lifting).
The second is an estimated annualised cost calculated over a six-year period. This doesn’t include labour and some coatings may last longer than their specified times, including the traditional ‘annual’ antifoulings, but we believe it gives a fairer reflection of the true cost over the long term.
Raymariner was repainted with fresh antifoul after our test ended in January 2022, but the static panel allowed us to see how the coatings fared 18 months since the test began.
It’s important to remember that a boat would not normally sit idle and uncleaned for that length of time, making the test more challenging for all our products but especially the ‘foul-release’ coatings which rely on water movement to help shift any fouling.
Now that the boat-based test has reached its conclusion, the static panel provided a valuable cross-check for the longer term performance of the products based on a visual assessment of the stripes, a finger swipe to see how easily any fouling came away, and a sponge wipe to check if the coating itself came away too.
Like the boat, our static test panel was immersed in a Portsmouth marina location in June 2021. Apart from the effect of the tide sweeping across it, the panel has remained in situ there, fully immersed at all times for the last 18 months.
As you can see from the pictures, the coatings have, by and large, performed extremely well. Apart from silty mud covering the test stripes, there are very few signs of serious fouling having taken hold on any of the coated sections.
Even green slime – highly prevalent when Raymariner was lifted a year ago – appears to have taken a back seat in this case, perhaps because the panel has been lying in a shaded area for most of the time. Proof of how well the coatings have performed can be seen by the growth of weed and up to 10cm long sea-squirts on untreated sections.
BEFORE (left): Copper colour turns a greeny blue once immersed. AFTER (right): Some slime evident but no weed or barnacles
Type: Epoxy-based non-eroding long-term biocide
Preparation: Hull-blasted back to bare GRP
Initial cost: £1,948 inc blasting & primer
Lifespan: 10 years+
Annualised cost over six years: £324
MBY rating: 4/5
Unlike the annual antifoul paints, which use a co*pound of copper suspended in eroding paint that gradually leaches out, Coppercoat uses pure copper powder set in a harder epoxy coating that should last for at least ten years.
It also vastly reduces the amount of copper released into the water, helping to prevent the build-up of copper in waterways, harbours and marinas.
Coppercoat can only be applied to hulls that have been stripped back to bare gelcoat and each of the five coats has to be applied wet-on-tacky. This effectively means it all has to be done during the course of a single day.
Lasts for 10 years, but has a high initial cost
Once dry, the surface needs to be burnished with 400-grit paper to expose and activate the copper. In future years, a pressure wash or scrub is all that’s required.
The results show a similar level of protection to the annual copper-based antifouls. There may be a little more slime than others but Coppercoat is a long-term solution and seven months is barely one season’s worth of use.
The initial cost is higher than most, partly because we have included the cost of blasting off the old antifoul (new boats just need sanding) but after six years the annual cost is much the same and it would continue getting cheaper after that. Nor does this take into account the substantial saving on labour time.
Before a thorough wipe-down (left) and after (right)
18-month update
Even though Coppercoat reco*mends an annual scrub or pressure wash to remove any surface growth, it still seems to be performing well after 18 months untouched. There was no significant fouling on the exposed copper surface, which has now adopted its characteristic blue/green colour, and minimal resistance from the swipe tests, suggesting any surface growth would fall away on a regularly used hull.
As expected of a tough epoxy based product there was no sign of the coating co*ing away on the sponge. Coppercoat’s claims of it being more environmentally friendly than erodible coatings.
Buy it now from coppercoat.c**
BEFORE (left): Smooth rubbery surface makes it hard for fouling to grip. AFTER (right): Impressive result – no weed, barnacles or even slime
Type: Non-biocide, silicone based foul-release coating
Preparation: Four coats Hempel Light Primer; one coat Silic One Tie-Coat
Initial cost: £1,045 inc primer and tie coat
Lifespan: 2 years+
Annualised cost over six years: £337
MBY rating: 5/5
Silic One has the most stringent application process of our group and is best applied to a stripped hull, unless the old antifouling is in very good order, when a barrier coat of Silic Seal will enable the switch.
The process starts with four thin layers of Light Primer, a tie-coat (applied while the primer is still tacky) and two coats of Silic One with a minimum of 8hrs in between, the last of which has a 16hr minimum drying time before re-immersion.
If it sounds like an involved process that’s because it is, taking nearly three days from start to finish once drying intervals have been factored in. However, the results speak for themselves.
Best performer, but fiddly to apply
After seven months, Silic One has performed the best of our group, with no signs of weed or shell growth and the least amount of surface slime. It also wiped off exceptionally easily.
Because it has a reco*mended lifespan of two years (but can last for up to five years) before it needs topping up with two fresh coats, the high initial application cost is offset over time. After six years its annualised cost is similar to many of the biocide products but could prove cheaper if it lasts longer than two years.
Before a thorough wipe-down (left) and after (right)
18-month update
We had expected foul-release coatings to struggle on a static panel without any movement through the water to shift surface fouling. However, the majority of the stripe stayed remarkably clean and any slime was easily swept aside with the swipe test.
Some isolated growth can be seen at the top of the strip but this could have been caused by migration of fouling from the untreated section in-between this and the Seajet Bioclean-Eko (the other products were separated by a strip of white Trilux antifouling). So far there are no signs of any surface deterioration.
BEFORE (left): Easy to apply and leaves a smooth finish. AFTER (right): Only a thin layer of slime that wipes off easily
Type: Soft eroding biocide antifouling
Preparation: Two coats Hempel Underwater Primer
Initial cost: £297 inc primer
Lifespan: 1-2 years
Annualised cost over six years: £166
MBY rating: 4/5
While it might not be the most technically sophisticated formulation out there, for many boat owners Tiger Xtra has beco*e a go-to product – a reliable staple and a firm favourite on the winter maintenance list.
With one of the highest per sqm coverage rates of anything tested here, applying Tiger Xtra will soon have you making decent progress across the hull in a relatively short space of time. The prospect of coating even larger than average hulls needn’t be as daunting or as expensive as you might have first imagined.
But does it work? The answer is yes. Doubtless, the regular, weekly use that Raymariner has been subject to these past seven months has helped get the best from all of our contenders (self-polishing mechanisms need movement of water across the hull) but on this evidence Tiger Xtra has performed as well as many of its more expensive rivals.
Impressive value, but needs applying every year
There was no weed or barnacle growth and the slime was a little easier to release than on some of the others. The only unknown quantity is whether this performance will continue over a longer length of time, especially if you’re cruising in warmer waters with higher fouling.
It represents such good value for money we have given it an extra star over its annual rivals.
Before a thorough wipe-down (left) and after (right)
18-month update
We were pleased to see how well the cheapest of our traditional antifouling coatings coped on the boat and the results from the panel did nothing to change this view. Our initial inspection showed no more fouling growth on this than any of the more expensive products and the finger swipe test easily shifted anything that was there.
Some of the coating surface colour did transfer onto the sponge, which is normal for a soft eroding coating, but over time it might start to wear through on a fast, regularly used boat.
BEFORE (left): Another easy to apply coating that leaves a smooth finish. AFTER (right): The usual layer of slime but a bit harder to shift than some
Type: Hard eroding biocide antifouling
Preparation: One coat Primacon
Initial cost: £444 inc primer
Lifespan: 1-2 years
Annualised cost over six years: £324
MBY rating: 3/5
Ultra 300 is a hard and relatively slow-eroding formulation that lends itself well to fast or regularly used motor boats that might wear through softer coatings too quickly.
After applying just one reco*mended coat of primer, we applied two good coats of Ultra 300, (total 120 microns dry), in a straightforward and fuss-free way, making life easy for the DIY applicator. Job done.
The results have been pretty good but marginally less impressive than the Micron 350, which Raymariner was coated with prior to this test, although that could be down to seasonal differences in water temperature and fouling growth rates.
Easy to apply, average performance
As expected, the Ultra was sheathed in a film of slime, thicker near the waterline, and when we tried to wipe the slime away with a damp microfibre towel, it showed quite a lot of resistance, suggesting it had taken hold quite firmly.
However, it was nothing that a jet-wash wouldn’t shift of course, and with no long beards of weed or shell growth to worry about. At an annual cost of around £324 for a typical 36ft boat it’s a solid, easy to apply performer that may last two seasons on lightly used boats.
Before a thorough wipe-down (left) and after (right)
18-month update
Although this is a traditional copper-based antifouling, it is a slow eroding hard coating designed for faster planing craft with increased water friction that might wear through softer products.
This didn’t affect its performance on our static test panel with little fouling growth over the 18 months and no sign of it starting to lose its antifouling properties. The swipe test suggests any fouling would fall away on a moving hull used regularly, while the sponge test showed only slight signs of the coating releasing itself.
BEFORE (left): Blue is one of several colours available in this range. AFTER (right): A decent result but not noticeably better than cheaper options
Type: Soft eroding biocide antifouling
Preparation: Four coats Jotun Megacote Epoxy; one coat Megasealer Epoxy Tie-Coat
Initial cost: £464 inc primer
Lifespan: 1-2 years
Annualised cost over six years: £355
MBY rating: 3/5
As we had stripped Raymariner’s hull back to bare gelcoat to ensure a level playing field for all of our products, Jotun decided to send us their full epoxy-primer, epoxy tie-coat and co*bined anti-osmosis system, prior to applying the two final coats of Jotun Non-Stop 2.
While this belt-and-braces approach would make sense on a brand new hull, we felt that for the purposes of price-co*parison, it would be fairer to use the cost of two coats of Jotun Vinyl Sealer – a straightforward, one-co*ponent product that we have been assured can also be applied on to bare gelcoat hulls.
As the name suggests, Jotun Vinyl Sealer is ideal for those looking to antifoul an already treated hull in good condition and is a readily available product the DIY user would be more inclined to buy.
Slime is easy to shift, but this antifoul is pricier than most
The results in January 2022 showed a good overall performance, broadly similar to the other copper-biocide products, with no significant weed or shell growth to talk about but a thickish layer of slime that shifted quite easily with the towel test.
Even if you opt to use only the basic vinyl primer for the initial application, the annualised cost still makes this one of the pricier options in our test so it will be interesting to see if it lasts longer than the cheaper options over a longer period of time.
Before a thorough wipe-down (left) and after (right)
18-month update
This premium priced self-polishing coating uses ion exchange technology to ensure a steady release of biocides throughout the year, even when the boat is not being regularly used. While it performed well it wasn’t noticeably better than some of its cheaper co*petitors.
However, it did have the highest degree of coating surface being released onto the sponge suggesting it was eroding consistently even without regular boat movement – a good thing as long as it has been applied in sufficient quantity.
BEFORE (left): Needs a good stir but paint goes on evenly. AFTER (right): Another solid performer with no shell or weed growth
Type: Soft eroding biocide antifouling
Preparation: Two coats Seajet 015 Primer
Initial cost: £489 inc primer
Lifespan: 1-2 years
Annualised cost over six years: £292
MBY rating: 3/5
When we heard about a new non-biocide antifoul release coating from Seajet, it made sense to co*pare it alongside Seajet Shogun, its best-selling, copper-based formulation.
Backed by the co*mercial resource of Chugoku Marine Paint, Seajet first appeared in the UK about 20 years ago and carved a niche for technical-quality antifouls.
One thing we found when applying Shogun is that the copper and zinc solids sink to the bottom of the tin so it’s imperative to ensure a good 5-10 minutes of continuous stirring with a wide-bladed stick – not the screwdriver you used to prise the lid off!
Solid performer, but needs regular stirring
The vapour given off made us glad we were outside in the fresh air but the coating itself goes on in a thick and consistent way. In keeping with the other biocide brands on test, close inspection showed a solid performance with no signs of shell or weed growth – just the usual slime, especially around the waterline.
The co*paratively high cost of the Seajet primer added a bit to the initial cost of application but in subsequent years the price co*es down considerably.
Before a thorough wipe-down (left) and after (right)
18-month update
Sold as a premium self-polishing annual treatment for boats capable of up to 40 knots in areas of high fouling growth, this antifouling treatment still seemed to be performing well after 18 months on our static panel.
There was minimal surface growth and only a light smattering of slime. As expected, a certain amount of blue coating did release onto the sponge when the panel was wiped, suggesting it will eventually wear through and reminding us not to skimp when applying this type of erodible coating.
BEFORE (left): Shiny silicone- based foul-release system is available in several colours. AFTER (right): Almost no fouling bar some migration of growth from the dividing strip
Type: Non-biocide, silicone based foul-release coating
Preparation: Three coats Seajet 117 Multipurpose Epoxy Primer; two coats Seajet Bioclean Tie-Coat; two coats Bioclean Eco
Initial cost: £1,012 inc primers
Lifespan: 3 years
Annualised cost over six years: £269
MBY rating: 4/5
Like Hempel’s Silic One, Seajet Bioclean Eco has a rubbery finish that fouling finds difficult to stick to. It is also a seven-coat system best used on bare gelcoat but can be applied on top of existing antifouling.
On bare gelcoat the process involves three coats of epoxy primer to provide a sound base, two coats of tie-coat, during which the colour element is introduced (black, white, navy-blue or red), then two coats of Bioclean-Eco – a transparent, paste-like substance.
When Raymariner was lifted, the majority of the test strip was admirably clean and shiny but there were some patches of fouling that appeared to have migrated across from the untreated dividing line separating this test patch from the neighbouring one rather than starting life on the black surface of Bioclean Eco itself.
3 year lifespan, but some fouling migration
Most of these dividing strips were painted with white International Trilux to avoid this happening but due to the longer application process of the silicone products we ran out of time on this one.
There was less slime than on the biocide products, and the wet microfibre towel test showed that it was easier to remove as well. Seajet expects this treatment to last for at least three years after which another tie coat and top coats should refresh it, although as this is a new product the reco*mended routine isn’t yet fully established.
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