- Toxic antifouling
- Antifouling systems and how they work
- Factors for the choice of antifouling
- Legal requirements for antifouling
- Correct application of antifoulings
- How to recognise the antifouling coating
- Preparation and care of the underwater hull
- Biocide-free antifouling alternatives
- Videos on the subject of antifouling
These are some of the questions that will be answered:
- When is antifouling necessary
- How often does antifouling need to be reapplied?
- What happens without antifouling
- How long does antifouling last?
If you take your boat out of the water after every use, you're in a good position. They don't have to worry about fouling. However, if the boat stays in the water for longer, the situation changes. The underwater hull must be protected from algae and other organisms so that the hull does not suddenly become overgrown with mussels and pox.
How quickly the fouling colonises depends on various factors - mainly the territory and the climatic influences on water temperature and salinity as well as the nutrient supply. User behaviour also plays a role. If the boat is stationary for a long time, it will colonise more quickly than a frequently moving vessel.
Toxic antifouling
But even constant driving does not protect against fouling. At some point, a biofilm forms that is no longer washed away by the incoming flow. This process can be slowed down by repeated, very fast trips, during which the fouling is washed off due to water friction, but it can never be completely prevented. The biofilm serves as a basis for further colonisation by smallpox and mussels. There are several strategies to prevent their spread. The classic approach is to use biocides, i.e. toxic substances that kill the growth.
Copper, which is present in almost all biocide-containing paints, is considered to be the main problem with the ingress of pollutants from boats. It reliably protects the hull against fouling by barnacles and mussels. However, the heavy metal also leaches out and enters the sea. How large the quantities released into the water are has been the subject of research for years.
In order to avoid spreading too much poison unnecessarily and still get through the season pockmark-free, the first question to ask when choosing antifouling is always: What are the fouling conditions like in your home waters? If you do not yet have your own experience, you can seek advice from the paint manufacturer or a neighbouring mooring. The Federal Environment Agency also provides detailed information on its website contains a vegetation atlas. It lists the creatures from which the hull must be protected in the respective area or harbour and which type of antifouling is recommended.
Antifouling systems and how they work
Factors for the choice of antifouling
The biocide content of the antifouling is one thing, but the colour must also match the owner's usage behaviour. Trailer boats and ships with shore berths that are regularly craned need robust antifouling that can withstand frequent watering; these are usually hard or thin-layer systems. Another decisive factor is how many months the boat spends in the water. If you want to sail until late autumn or even leave the boat in the water over the winter, you should definitely tell the seller, as the manufacturers determine an average service life for boats that does not necessarily correspond to the individual owner's preference.
The same applies to boats that lie unused in the harbour for a very long time: In this case, paints with an even biocide release make sense; self-polishing products are not the first choice. However, these are recommended if the boat is regularly moved.
Of course, the material of the boat must also be clarified: aluminium boats in particular do not tolerate many of the common antifoulings, as copper compounds are usually used as biocides. This can lead to electrolysis!
There is also the question of how much labour is considered acceptable. With hard antifouling, the old paint layer usually has to be sanded down every year. On the other hand, there are also coatings that only need to be touched up every other winter. A copper epoxy coating such as Coppercoat gives you even longer peace of mind. The manufacturer states a service life of around ten years - in our experience, this is a very realistic figure.
Legal requirements for antifouling
Last but not least, it is important to observe the legal regulations for the respective area. In Germany, only the deviating regulations for inland areas are of interest, where coatings containing biocides are often prohibited. Stricter regulations often apply abroad, but this only affects permanent residents.
In the Netherlands and Sweden, the antifouling must have special authorisation. Theoretically, you can find out which products these are on the websites of the respective approval authorities. In practice, the websites are only helpful for native speakers and you should ask the paint manufacturer for proof of the necessary approval. In Holland at least, the authorities are very active and monitor the use of paints. Recently, they have even gone so far as to check the copper content of the antifouling in the water. If they come across a banned product, they face a fine of 2,500 euros.
Correct application of antifoulings
The question of correct processing remains. The effect of any antifouling wears off over time. Depending on the product, coating thickness and fouling conditions, repainting is necessary every one to two years. If you know what the hull is painted with and don't want to change the product, you can start preparing immediately. If the old paint is unknown, it is important to ensure compatibility with the new antifouling. To do this, the colour type must first be determined.
A simple test can clarify whether a self-polishing or hard antifouling is present: If the polishing product is rubbed off with a damp cloth or sponge, traces of colour will remain. Hard antifouling shows virtually no removal. Thin-layer or Teflon antifouling can be recognised by the almost lacquer-like, significantly smoother surface.
Self-polishing and hard antifoulings can usually be painted over directly together. If in doubt, however, a layer of primer matching the new paint should be applied. It is more difficult with Teflon paints. These are only compatible, if at all, with another thin-film antifouling. In this case, you must ask the previous owner or shipyard for the exact type of paint.
How to recognise the antifouling coating
Depending on the antifouling system, the procedure for reworking differs. In addition, not all paints are compatible with each other. The colour type can be determined with a simple test:
Preparation and care of the underwater hull
Whatever the choice, the underwater hull must be thoroughly cleaned to prevent the paint from flaking off after just a few seasons. A high-pressure wash in autumn is not enough. Oil residue almost always collects, especially at the waterline. A follow-up wash with a Scotch-Brite or abrasive sponge and clean water will achieve the desired result.
If you want to be on the safe side, add a cleaning additive to the wash water as a grease remover. The rough surface of the sponge is sufficient as a pre-treatment for self-polishing paints. Hard antifouling requires a little longer scrubbing; the washed-out colour surface must be removed. Antifouling should never be sanded dry - the unavoidable dust is harmful to health.
During the wash cycle, you should check the underwater hull: Is the old paint still firmly in place? If there are large areas of damage, a complete repaint is actually necessary. With a special epoxy primer, for example from Vosschemie, even a dilapidated paint structure can be stabilised to such an extent that it will last a few more years. The product is appropriately called Antifouling Anchorage.
Biocide-free antifouling alternatives
A more environmentally friendly approach would be frequent mechanical cleaning using a boat washing system in combination with a non-toxic coating. However, these techniques are not yet mature or widespread enough to be a serious alternative to chemical fouling protection for boats in saltwater areas.
Silicone-based fouling release systems such as Silic One from Hempel or the films from Mactac and Renolit, which work on the same principle, are more promising. They also work without biocides. Instead of killing the growth, the smooth coating impairs adhesion, so that pocks and the like are washed off when driving. They also create a so-called hydrogel surface, which appears like water to smallpox and mussel larvae; the hull of the boat is virtually hidden behind it as a settlement area. However, frequent and sufficiently fast sailing is required for the fouling to dissolve by itself; around seven to ten knots is ideal. In addition, the soft silicone surface is sensitive and can easily be damaged when craning.
For most areas, paints containing biocides are the safest and most convenient way to keep the underwater hull permanently clean. Even if suppliers of non-toxic systems often claim the opposite, a complete ban on products containing biocides is not in sight. It is true that EU-wide efforts have been underway for years to restrict the use of biocides in order to reduce the environmental and health impact. This affects insecticides, plant and wood preservatives as well as antifoulings.
The procedure is multi-stage and extremely lengthy. Manufacturers must register active ingredients and formulations and have them approved individually. The antifouling products are currently in the registration phase - in other words, only registered biocides may be marketed and used. They are given a registration number and a temporary authorisation until a final risk assessment has been carried out. The list of authorised active substances in product group 21 can be viewed on the website of the Federal Office for Occupational Safety and Health (BAuA).
