Everything you ever wanted to know about antifoulings


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you dry-dock the boat frequently, you will not be able to do without giving the hull a good antifouling treatment. And not only because algae and fouling (as a whole, referred to as “biofouling”) reduce a boat’s performance and increase its consumption: in fact, they can progressively affect the structure of the hull by damaging it (e.g., by osmosis phenomena).


Antifouling paints owe their effectiveness to the presence of biocides (the most widely used is copper oxide; tin has been outlawed for its high polluting power), which 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, the most famous being Seventy by Veneziani) or innovative ones: some products, for example, contain micro-particles of carbon in such a way as to create an extremely smooth protective film, ideal for racing boats. We will also tell you about paint-free solutions later. Based on their composition, antifoulings are divided into two major families: self-polishing and hard-matrix.

Life cycle of a self-polishing antifouling.
Life cycle of a self-polishing antifouling.

Self-polishing 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 are not suitable for ultrafast hulls, but they are fine for cruising boats. Moreover, precisely because of the progressive thinning, at the end of the season, once the boat is hauled out, removing the leftover layers with a pressure washer is a breeze.

antifouling-paintsHard matrix products, unlike self-polishers, act only chemically. Based on a polymer-type binder (often acrylic or vinyl in nature) they are very resistant to abrasion, so they are an optimal solution for vessels 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. 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.

Special attention should be paid to propellers and metal parts: specific antifoulings are needed to avoid galvanic corrosion phenomena
Special attention should be paid to propellers and metal parts: specific antifoulings are needed to prevent galvanic corrosion phenomena.

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 that can seriously damage the hull. This is precisely why all antifouling manufacturers offer paint ranges specifically dedicated to the protection of metal hulls, sail drives, bulbs and propellers.

Screenshot 2016-03-15 at 4:41:47 p.m.
In the table above, the approximate amounts of antifouling paint as a function of hull length.

To calculate the amount of paintable surface area of the hull we can use this formula: [A x (B+2C)] x 0.4 where A is the waterline length, B the maximum beam and C the draft; 0.4 is the generic hull curvature coefficient for sailboats. Let’s take 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). In this case, the paintable area will be 33.8 square meters. Having obtained the value of the paintable surface, we will need 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). Now you will simply divide the area by the yield. Still returning to our Oceanis 40, then, to cover the entire hull with antifouling we will need 3.38 liters. Since the recommended number of coats is two, you will just have to double the result: in this case 6.76 liters (see table for approximate paint quantities based on hull length).

The planet of antifouling paints. Self-polishing, hard-matrix, environmentally friendly-that’s who to rely on for a consistently top-notch hull.

stoppani logoSTOPPANI
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 new universal antifouling paint that is extremely pliable and effective. www.lechler.eu

Hempel celebrated 100 years in business. The Danish brand’s antifouling products (both self-polishing and hard matrix products) are composed of a resin matrix that dissolves in a controlled manner, totally eliminating the presence of vegetation on the hull while preventing the release of harmful substances. www.hempel.it

Screenshot 2016-03-15 at 5:06:43 p.m.JOTUN
The Norwegian giant offers NonStop self-polishing 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 . www.jotun.it

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. www.cecchi.it

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

Other major manufacturers




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