THE BIG ANTIFOULING TEST

It's easy to become confused by the sheer number of antifouling paints on the market. How do you choose one over

another? What are the differences between them? Does high cost guarantee high performance?
 

To find out the answers to these questions we decided to test a range of antifouling products.

Ten eroding antifouling ‘s spent last season in the murky waters of the East Coast, South Coast and West Country. Those we have tested are merely a selection from a massive market – it was logistically impossible to apply this real life test to every antifouling product available.

The antifouling were applied individually to test boats at the start of last season, and to one boat that was divided into sections for a sample of each paint. The bow and stern sections of the hull were discounted from the test as waves and the prop may have an unfair effect on those areas. All of the antifouling products were applied according to the manufacturer’s directions, and the boats were given two coats.

At the end of the season the boats were lifted or dried out for inspection and photographed. The results of the tests were based on the multiple test boat. Sweet Lucy 111, which was painted with a sample of each antifouling. The results of the other test boats were compared with these, ensuring that no disparity was overlooked.

Antifouling Facts
Antifouling must be strong enough to inhibit the growth of biofouling, which would otherwise reduce a boat’s performance, without polluting the water beyond acceptable levels. It must be effective against a vast range of organisms such as protozoa, marine fungi, algae spores, limpets, barnacles and seaweed in a variety of conditions.

It must withstand the erosive forces of water, scrubbing, powerwashing and drying-out. And it should manage to do all this for at least one season.

Most antifouling paints are based on toxicants derived from heavy metals. Copper, or cuprious oxide, which is a copper compound, is found in varying quantities in many antifouling products using binders to keep it in suspension. The copper acts as a biocide, the quantity of which however, does not dictate the effectiveness; it simply indicates how long the antifouling will last. The effectiveness is dictated by the amount of copper that is released, or leached.

There are several types of antifouling paints. Ablative or soluble paints (also known as soft-eroding, self-polishing or co-polymer) work by slowly eroding and exposing copper, which then dissolves. The process is continuous, and therefore the thickness of paint determines its life.

Conventional paints, often known as hard antifouling, work differently. The paint itself does not erode. Instead the copper particles on the surface dissolve, to reveal new copper particles. These are designed for racing boats and are not included in our test. Copper-epoxy antifoulings consist of copper powder suspended in epoxy; they are costly, but are claimed to last for many seasons. (See YM test feature next month)

It might be tempting to slap some highly-toxic paint on your hull that nothing would dare to come in contact with, but in today’s climate this is not acceptable. Since tin-based TBT paints were banned over a decade ago antifouling paints must conform to stringent regulations.

Biofouling is ‘an undesirable accumulation of micro-organisms, plants and animals on artificial surfaces’. There are four stages to marine biofouling, the first of which occurs as soon as an artificial object is immersed. The surface rapidly accumulates organic matter, polysaccharides and proteins. Bacteria settle on this layer, forming what is known as a microbial biofilm, secreting chemicals that cause corrosion and eat away organic materials. The third stage involves the attraction of organisms such as protozoa, marine fungi and algae spores, which settle on the biofilm. Finally, invertebrates, such as limpets and barnacles, together with algae and seaweed, attach themselves to the surface creating a small, yet complete, community.

Flag Flagship (Tester: Dufour 30, Hasler)

* * * * * * * * * *
Type: Self-polishing
Thinners: Flagship thinner
Min working temp: Unspecified
Over-coating: 6 hours
Launching – Min: 12 hours
Max: 2 months
Max dilution: 10%
Application: Brush, roller, pad, spray
Coverage (m²/lit): 10

Ease of Application:
This was the best product to use with a good balance between easy application and film thickness. It flows out well and is easy to work. Colour was reasonably even after the first coat.

Build-up Rate:
One of the best.

Performance:
Moderate layer of slime without any other growth. Residual coating was also moderately thick, but would need re-coating for another whole season.

The Verdict
Although the antifouling paints we tested performed differently, it would not be fair to put too much emphasis on one being markedly better than another. None of the antifoulings performed badly; indeed, all did the job for which they are intended. A thin coating of slime will not reduce a boat’s performance in a cruising context.

Weed, limpets and barnacles, however, would be detrimental to performance, but, apart from a slight skirt of weed on the waterline that may have been due to a very thin coating of antifouling on the boot top, all of the antifoulings were effective against them. However, the rate and level of biofouling depends very much on water temperature, salinity, flow, sunlight, and levels of phosphates and nitrates.

An antifouling which performs well in one situation will not necessarily perform as well elsewhere. While the results don’t reveal a huge disparity between the antifoulings, there are a couple of trends worth noting. The Solent, in general, does not suffer from high levels of fouling.

Flag’s Flagship, which is second to none for application, and Teamac’s D Type antifouling, both retailing at about xxxxxx , represent excellent value for money, and do as good a job, if not better, than antifoulings costing more than twice as much. The ‘premium’ products, as a whole, did not perform as well as the less expensive, and perhaps less well known brands. Nevertheless, while the premium products tended to have a thicker residual coat, that would probably last for another season, the less expensive products would require over-coating.