Antifouling – The Hows And Whys

Post by: Dee White
05 April 2013

In my previous article – "Stowaways – The Marine Creatures Hitching A Lift On Your Boat", I described some of the various invasive species taking advantage of your pride and joy. Here are some tips and advice about getting rid of them so that you can enjoy your boating.

Some History

It was Plutarch who first mentioned the impact of fouling on a ship's speed when he wrote about the "weeds, ooze and filth" which stuck onto its sides. The ships of Carthage and Phoenicia used pitch and copper plating techniques to combat the problem from 1500 – 300 BC, whilst wax, tar and asphaltum were also used in early times and even a mixture of arsenic, oil and sulphur.

In 1761 experiments were made with copper sheathing for vessels. This worked well in protecting the hull from organisms and weed as the copper produced a poisonous film when it came into contact with the water which deterred the marine creatures. It was so successful that the British Royal Navy proceeded to copper the bottoms of their whole fleet of wooden hulled vessels.

The first experiments with anti fouling paints began in the 19th century when copper could no longer be used on the new iron hulled ships. The first to be used was the "McIness" hot plastic paint, but this had a short life and was expensive and ineffective. By the middle of the 20th century copper oxide paints were being used, but these too were not particularly effective as some invasive species seemed to be immune and there were concerns about water pollution.

In 1960 there was a breakthrough with self polishing paints which released stored toxin at a slow and controlled rate. These paints used tin-based biotoxins such as Tributylin (TBT) which killed the micro-organisms and were effective for up to 4 years. It was discovered, however, that they had an extremely adverse effect on marine life and human health and there was a worldwide ban on their use by the International Maritime Organisation (IMO) who adopted the International Convention on the Control of Harmful Anti-fouling Systems on Ships, which came into force on September 2008. Antifouling products are covered by a variety of different regulations because of their connections with hazardous substances, pesticides, Health and Safety and Biocidal Products.

Non-toxic coatings seemed to be the way to go. These were usually based on organic polymers and created a smooth surface, making it difficult for the organisms to attach. Test results in America support the practice of using non-toxic coatings and frequent cleanings with the gentlest, effective cleaning tool. Another innovation, which could replace paint, is the use of a mesh which covers the hull, underneath which a series of pores supply a slime compound. This constantly sloughs off and carries away the offending organisms. Other tests carried out in California found that the toxic copper-based antifoulants were more successful than the non-toxic ones which required more abrasive tools and effort. Also longer cleaning intervals allowed organisms to mature and become much harder to remove. This sometimes resulted in chipping and scratching of the paint, providing an ideal surface for new growth.

In my research I have found that the most popular brands currently available use self-polishing, copper-based copolymers which can be used on GRP, wood, steel or ferro-cement hulls. The copper does not act as a poison like the banned TBT, but reacts with the sea water to create charged particles which create an environment which the organisms cannot adhere to.

A new antifoul paint is being developed from the fluoro-polymer presently used by many British and American ships. It creates a surface too smooth for creatures to grip onto, but at present it only is successful when vessels maintain an average speed of more than 8 knots. The scientists hope to produce a version suitable for slower vessels, but there is still likely to be some sort of speed requirement and it is unlikely to be suitable for leisure boats that spend a large proportion of their time stationary.

A completely different method of antifouling is the use of electrical pulses. Pulsed laser irradiation has been commonly used against diatoms, plasma pulse technology is effective against zebra mussels and build-ups of algae have been treated with high energy acoustic pulses.

What Can I Do About It?

  • Inspect and clean your boat regularly, especially before you leave port.
  • Regularly apply antifouling paint according to the manufacturer's recommended timeframe.
  • Use manual cleaning but do not rely on this alone. You need to apply antifouling paint in conjunction with manual cleaning.
  • Dispose of all fouling organisms in a safe way. Do not leave them to be carried away by the next tide.

Where Should I Clean My Boat?

There are many theories put forward about where boat cleaning should or should not be carried out. Some people maintain that toxic chemicals are released from soft coat antifouling paint when you disturb it by cleaning and they are of the opinion that any cleaning of them should be carried out well away from the water. On the other hand, hard coats and epoxy-based coating seem to be safe for in-water cleaning. They discourage orgasm growth, last for longer and minimise harm to the environment. Just to confuse matters, some Australian research suggests that some in-water cleaning practices actually stimulate fouling growth.

How Do I Do It?

The easiest thing to do is to arrange to have your boat lifted out of the water and put safely on blocks and props so that you can work underneath it. It then needs jet-washing with clean water. You may be able to get the boatyard to do this rather than do it yourself.

First check the hull for signs of damage, blistering or cracking and repair if necessary using watertight epoxy filler. Remove any loose or cracked coating, pressure wash to make sure you have a good surface to work on and allow it to dry completely. Decide what type of antifoul you are going to use based on what is suitable for your particular boat, the area where you intend to use it and the type of hull. Also remember that it must be compatible with the paint already on the hull. With a job such as this, you don't want to put yourself into the position of stripping it all off and starting again. There are so many brands on the market that choosing a suitable one may seem daunting and it is worth getting advice from other boat owners and going to a reputable manufacturer who will supply you with free technical advice.

On new boats antifouling paint cannot be applied directly onto the hull without keying it by sanding it down and priming. If there are layers of existing antifoul paint underneath you should ensure that the new treatment is compatible and apply primer first if you have any doubts. Check details about time between coats and between painting and relaunching. Many people use the winter months to carry out their antifouling so it is sensible to keep your cans of paint indoors as application is easier if the paint is not too chilled.

Wear protective clothes such as overalls, gloves, hat, mask and eye protectors and work in an open environment. Make sure that the paint is stirred well, as the heavy copper tends to settle at the bottom. The usual application method is with brush and roller. Use a roller suitable for gloss paint as they tend to be more hard wearing. Apply at least two coats and more around the waterline where there will be turbulence. It is important to ensure that all areas of the boat are completely covered and that the paint is thoroughly dry before immersion. Some manufacturers will advise you that the paint can be thinned if drying conditions are quick. On a warm windy day the paint will dry faster but the finish will not be so good.

Job Done

Now you can sail off into the blue, reasonably secure in the knowledge that the parasitic army of marine organisms will leave you alone. Well….until the next time. Then, I'm afraid, the whole business starts again. But hey – that's what boating is all about – isn't it?

Author – Dee White

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