INTERVIEW TO ANTIVEGATIVE The number one ally of your hull


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Antifouling. Which ones to use, how and why to use them, the right quantities, costs, the market, their history, and alternative solutions. In the form of an “interview,” we dissected a vital issue for boaters who do not want to find their hull battered by algae and fouling like the one pictured above.


What are antifoulings?

Simplifying as much as possible, we could define antifouling paints as a coating designed to inhibit the growth of marine organisms (biofouling) on the submerged surface (living work) of boats through the controlled release of biocidal substances. They normally consist of one or more biocide substances (the most common is copper oxide; tin has been outlawed because of its high polluting power), a binding resin (holds the product together by creating the paint film and controlling the release of the biocide), a solvent (which allows it to be spread evenly on the boat), and a pigment (which characterizes the color).

Only in the spot not attacked by mussels and dog teeth was antifouling used

Why is it advantageous to use them?
The benefits of using these products are obvious: Preventing or reducing fouling caused by animals or vegetation, ensuring minimal friction, and maximizing boat speed and performance, reduce fuel consumption and prevent dirt from penetrating under the paint layer and improve hull protection.

Graph explains the formation of fouling over time

What are the “enemies” that antifouling paints fight against?
The word “biofouling” generally refers to all organisms that attach and grow, more or less visibly, under your boat. Suppose the boat is launched without antifouling layers: a layer of glycoproteins and polysaccharides is formed already in the first few seconds of immersion in the water, altering the chemical and physical properties of the surface. Soon after, bacteria arrive and form the “biofilm,” which will form the “base” for more complex organisms to take root. After a few hours, diatom (single-celled) algae and protozoa also creep in. In the first few weeks, organisms such as algal spores and animal larvae (including barnacles, these attack even if the boat is sailing at 5 knots of speed) arrive. In the final stage (between six months and a year after the “careless launching”) you will have the hull studded with adult barnacles (so-called “dog’s teeth”), mussels, worms and algae (usually green in the brighter areas of the live work, brown in the darker areas such as near the keel). A curiosity: the great naturalist Charles Darwin studied barnacles for so long that he ended up hating them. “I hate barnacles more than any other human being, more than a sailor aboard a boat that sails very slowly.”

And if I keep the boat at the lake, should I equally apply antifouling?
In fresh water, generally, the formation of algae and fouling is much “milder” than in the sea.
Many boat owners dry-dock the boat at the end of the season and notice a light layer of green algae that comes very easily, but it has also happened to be faced with more leathery organisms. In any case, if you keep the boat in the water, it is advisable to treat the hull, perhaps with a water-based antifouling.

Growth intensity of organisms decreases with increasing depth and distance from the coast

What factors influence the growth of organisms and fouling on the living work?
There are five factors that combine to determine how fast biofouling grows under your boat: the temperature of the water (the hotter it is, the more we will see growth phenomena), The depth and distance from the coast (as both increase, organisms will have more difficulty proliferating), The presence of nutrients and exposure to sunlight. As an illustration, look at the wreck of the Titanic: it “defended” itself really well in more than 100 years on the seabed, in total darkness and cold, at a depth of 3,800 meters!

How do antifouling paints work?
As mentioned, antifouling paints owe their effectiveness to the presence of biocides that are released into the environment in a “controlled” manner so that they are active only in the vicinity of the boat, limiting pollution as much as possible.
There are “eco” paints (such as water-based antifoulings) or innovative ones: some products, for example, contain carbon micro-particles in such a way as to create an extremely smooth protective film, ideal for racing boats. Based on their composition, antifoulings are divided into two major families: self-polishing and hard-matrix. They can also be single-component or two-component: l e first consist of a single component and the formation of the antifouling film occurs by oxidation or evaporation of the solvent-they are easy to apply but lose quality over time. Two-components, on the other hand, consist of two components that can be mixed according to predetermined proportions (one of them usually being the catalyst) Film formation in this case is possible due to the chemical reaction between the two components, giving greater strength and durability to the “aesthetic” factor.

The working principles of antifoulings explained by Jotun

What do self-polishing paints consist of and what boats are they good for?
antifoulings (also referred to as water-soluble or self-cleaning), in addition to being chemically active, also count on a “mechanical” effect: this type of paint gradually absorbs water causing a gradual dissolution of the matrix. The chemical action of the water and the mechanical action of the boat’s movement regenerate each coat of antifouling spread (the so-called ablative action). Renewal occurs on the order of microns, so there is no risk of the paint wearing off completely during the season. Self-polishers did not go to ultrafast hulls, but they are fine for cruising boats. Moreover, precisely because of the gradual thinning, at the end of the season, once the boat is hauled out, removing the leftover layers with a pressure washer is much easier.

What about the hard matrix ones?
Hard matrix products, unlike self-polishers, act only chemically. Based on a polymer-type insoluble binder (often acrylic or vinyl in nature) they are very abrasion resistant, so they are an optimal solution for boats that are winged and carted frequently, or very fast. Generally, they have lower costs than self-sanding paints and suffer less from changes in water conditions (temperature, salinity, currents), so they are also suitable for long-distance boaters. In contrast, the biocide release rate is not constant, and product performance gradually decreases during the season. Then there is a third type of varnish, mixed-matrix (or hydrophilic) antifouling, which resists UV rays well and offers excellent flow quality, and is suitable for performance hulls.

If I had a metal boat what antifoulings should I use?
Hulls made of aluminum, steel, or iron and generally all metal surfaces require special care, because spreading paints containing metal biocides on them could trigger galvanic corrosion processes capable of seriously damaging the hull
. This is precisely why all antifouling manufacturers offer ranges of paints expressly dedicated to the protection of metal hulls, sail drives, bulbs and propellers: they are usually not based on copper oxide but on less “noble” materials capable of generating lower galvanic currents (zinc pyrithione, copper thiocyanate). Regular antifoulings may also be fine, but you must be sure that the primer layer (read below) applied to the hull is uniform and truly insulating.

What is primer?
Primers are defined as “anchoring” products for antifouling: they have important protective functions of the hull, whether fiberglass (to prevent osmotic phenomena) or metal (to protect it from corrosion). Even on wooden boats, it is a good idea to use dedicated primers before applying paint. The primer should be applied on the new boat as soon as it leaves the yard, but also (this happens often for used boats) if you are unsure of the “compatibility” between the previously applied primer or antifouling and the antifouling you want to apply. As a rule, antifouling paint manufacturers provide compatibility tables.

How should antifouling be applied?
If you have decided to do the antifouling operations yourself,
initially you will need to thoroughly clean the hull and appendages to remove any traces of sand, grease, tar and previous coats of antifouling, perhaps using a pressure washer and degreasing products (which we will need to remember to rinse off!). To make it easier for the product to take root, you will then pass a quick coat of fairly fine sandpaper (such as P180), and then remove the dust with the help of a hard-bristled brush. Please note: if a self-sanding product was previously applied there should be no problem in its removal, but should you be faced with an exhausted hard matrix paint, in this case it will be more cumbersome to remove bubbles and flakes.
If the layer that has accumulated over the years shows signs of deterioration, and therefore there is a risk of impairing the hold of the new antifouling, it will be advisable to remove it completely (either mechanically or through a chemical painter) and apply a new primer. Mark off the area to be sanded with tape to avoid ruining parts of the boat that will not be covered by the paint. If you use a power tool, act with “light” and quick passes without insisting too much on one area and risking ruining the gelcoat (at the end of the operation, pass the hull with fine-grained sandpaper so as not to leave the hull too “rough”). The hull is now ready: mark off the paint area with tape (as well as other places that will not need to be painted, such as any sacrificial anodes) and apply two coats of product, generally 2-3 coats apart.

An additional hand, customarily, should be applied at “hot” spots such as the waterline, rudder blade and stern foot. To preserve propellers, there are specific products (such as some antifouling sprays). all antifouling manufacturers offer paint ranges specifically dedicated to the protection of metal hulls, sail drives, bulbs and propellers. Don’t forget to use gloves (required by law) and a protective mask, and you will also need to affix a nylon sheet under the boat in the shallows to preserve the environment. Avoid application in adverse conditions such as strong wind, under direct light or heat sources (especially midday in summer), low temperatures, high humidity or rain. For application, you can use a medium-short-haired roller: for small areas or touch-ups, you can use a brush but it must be solvent-resistant. It is important to use a good quality brush so that its fibers are not scattered on the film of the applied product. Application by spray, on the other hand, is something usually done by professionals.

How much should be applied?

There is a fairly precise formula for calculating how much antifouling you will need based on the size of the hull, i.e., paintable area divided by yield
. To determine the paintable surface we will have to perform a simple mathematical operation: [A x (B+2C)] x 0.5 where A is the waterline length, B is the maximum beam and C is the draft; 0.5 is the generic hull curvature coefficient for standard keel sailboats (0.75 for long keel boats). Having obtained the value of the paintable surface, we will have to calculate the actual amount of antifouling based on its yield. The yield, on average, is 10 square meters per liter of product (however, it is indicated on each package).
Better to give an example: let’s take a 12-meter cruiser that is widespread in the market, such as the Oceanis 40 (10.35 m at waterline, 4.37 wide and with 1.90 draft). Let’s calculate the paintable area: [10,35 x (4,37+3,80)] x 0.5 = 42.27 sq. m. Now we divide by the yield and get the gallons needed, 4.22. Finally, we multiply the result by two since, generally, two coats of paint must be applied to the hull and we will know that an Oceanis 40 will need 8.44 liters of antifouling.

If I hire a professional to apply antifouling (a recommended choice), how much will the complete job cost me?
Generally, for a 12-meter boat, prices (only related to hull refit) fluctuate depending on the area, but indicatively we will be between 1,400 and 2,000 euros for hauling, launching, handling, laying of notches, washing, abrading, application of two coats of antifouling, grounding for the duration of the work.

Coating the hull of a sailing ship with copper sheathing

What is the history of antifoulings?
Early solutions to protect the living work of boats have their roots in history: as early as 412 B.C., in an Aramaic papyrus concerning boat repair, there is mention of a “mixture of sulfur and arsenic” that, when applied to the bottom of the boat, makes it glide fast over the water.
In the third century B.C. the Greeks used tar and sear to cover the hulls of their ships, but it was between 1200 and 400 that the use of oils, resins, and animal fat became widespread. Chinese admiral Zheng He (1371 – 1434) had his junks lined with lime mixed with poisonous oils to prevent the proliferation of worms. Christopher Columbus had also had his hulls coated with a mixture of tar and animal fat to ward off fouling: the navigator recommended that the sailing ships should then be tilted on a convenient beach periodically for the compound to be re-spread.

The sailing ship “Formidable” lying down during hull refit in Malta

In the 16th century, the main form of protection for wooden ships was a copper sheathing or a mixture containing sulfur and arsenic. Copper covering was later abandoned with the appearance of iron hulls. In 1625 William Beale was the first to file a patent for a paint containing iron powder, copper, and cement, while 45 years later Philip Howard and Frances Watson patented a paint of tar, resin, and beeswax. Toward the end of the 18th century was the turn of William Murdock, who patented a paint mixed with powdered iron sulfide and zinc, using arsenic as an antifouling agent.
But the 1800s is the real “antifouling century.” with over 300 patents registered as of 1870: then, as now, the basic principle of most antifouling paints was to use one or more biocides to discourage the establishment of fouling organisms through a release mechanism (which would later become “contact” in the second half of the 1900s).

Are there alternatives to antifouling paints?
Especially in recent years, there has been a proliferation of alternatives to traditional antifouling paints
, which have been “accused” (often wrongly) of being polluting and expensive (since, on average, they need to be applied once a year). One consists of wrapping the living work: a series of adhesive and antifouling films. The advantages, in theory, are many: compared with paint, whose effects fade over time, self-adhesive film is more effective, causes less friction and does not pollute. Of course it is not a job you will be able to do yourself, it takes a professional, and the costs are not low. Then there is the possibility (after sanding the hull down to the shell), of giving several coats of resin mixed with some copper powder, biocide par excellence. In theory, the longevity of the treatment and the smoothness of the hull are guaranteed: the disadvantage is the extreme difficulty of sanding and returning to the original shell if the operation were to be repeated. If you don’t want to use antifouling products, you can rely on cleaning on rollers car-wash style: a system that is not very popular for now, and moreover may not work for boats with double rudders or keelboats. Or you can, when the boat is moored (if you have a lifting keel system), install a protective surface that, by keeping the living work in the dark, limits the colonization of organisms. As can be easily guessed, these are not “universal” solutions: traditional antifoulings have the strength to be effective on any kind of hull. Finally, we mention ultrasonic systems, which emit frequencies from a transducer directly immersed in the water, preventing the development of fouling and algae when the boat is moored.

What are the major antifouling manufacturers?
Below you will find a list of major international antifouling paint manufacturers.

Among the many products, the Norwegian giant offers NonStop self-sanding paint, formulated with advanced moisturizing binders, which ensures a constantly renewing active surface. Racing paint, on the other hand, is hard matrix and gives a hard, smooth and polishable surface. Also an interesting solution is Aqualine Optima, a spray paint for protecting motors and submerged metal components .

are the products offered by Veneziani, including hard-matrix, self-polishing and two-component antifoulings Famous is Raphael, very special and environmentally friendly is Seventy, a water-based paint to meet the latest and strictest regulations in an environmental manner. It protects the hull from algae and all kinds of freshwater and saltwater marine life.

Boero YachtCoatings manufactures high-quality paint products for any use in the nautical field and has been, for decades, a reference for the Italian and international market, satisfying at best the demands of the passionate yachtsman as well as those of the professional involved in the construction of ambitious yachts and superyachts. Among its flagship products, it offers Magellan 630, an antifouling with innovative SPC technology that provides an extremely smooth, fully self-polishing film with constant release, top-quality performance and optimal protection for up to 36 months. This antifouling uses biocides that are already in line with the future European Biocide Product Regulation (BPR) and was chosen by Giovanni Soldini and the Maserati team for the new multihull Multi 70.

International is a leading European supplier of marine paints that help protect, beautify, and enhance the performance of all types of boats. Among its flagship products is the premium multi-seasonal antifouling with innovative patented Micron“Water Activated Matrix” technology for minimal environmental impact. Ultra 300, on the other hand, provides a hard matrix formulation for areas of high biological density.

Since 2007, the historic Stoppani brand has been part of the Lechler Group: among its self-polishing antifoulings particularly suitable for sailboats is Sibelius Active. Among those with a hard matrix, Sibelius Light Endurance is the universal antifouling paint that is extremely pliable and effective.

Among self-polishing paints, Cecchi offers Nautilus Self Polishing ideal for those who always want more than smooth surfaces. Free of metal salts, it is also good for aluminum and light alloy hulls. The paint reduces its thickness during the season, and once you pull the boat dry, a light wash and reapplication will suffice.

Other major manufacturers

edited by Eugenio Ruocco


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