Environmental good practice and antifouling need not be the opposite ends of the spectrum. But do you know how to choose the right antifouling, apply the right quantities, carry out that mid-season scrub and remove and dispose of the old coatings? Hopefully we can shed some light on the issue.

What s in antifouling?
The majority of antifouling paints produced in the UK are copper-based, in which the main biocide is cuprous oxide, the natural form of copper. The paints also contain other biocides in smaller quantities, know as booster biocides. Some paints are made up with a biocide called cuprous thiocyanate, which contain a less potent form of copper and these can be referred to as copper free paints. However, cuprous thiocyanate-based antifouling paints are generally not as effective or long lasting as the copper-based biocides. The biocide used is always displayed on the label of the tin and in the technical information associated with the paint.

Increasingly we are seeing non-toxic coatings being developed. Whilst they will not inhibit growth of marine organisms on the hulls of boats, they are designed to be cleaned easily, even as the boat is used. 

What does cooper do in the marine environment?
Although copper occurs naturally in the environment, too much can damage both plants and animals. Copper in the dissolved form is potentially very toxic to aquatic animals and plants, especially to young life-stages such as fish larvae. The toxicity of copper is reduced when it is bound to particulate matter in the water and sediments. 

Self polishing, hard racing or slimy?
Erodible or Self-Polishing paints are the most widely used type of antifouling paints amongst recreational boat owners. They work by the paint surface adjacent to the water dissolving, removing any organisms that may be clinging to the hull and exposing a fresh layer of biocide to combat any further fouling. Because the surface of the paint is unstable it is difficult for organisms to establish a firm hold and consequently less biocide is needed within the paint matrix to produce the required affect. Most of the original paint is washed away as the boat is used throughout the season, resulting in far less build up over the years and less work for the owner when it comes to reapplying antifouling.

Hard paints contain high levels of insoluble resin, producing a paint matrix that does not erode on contact with water. The process by which these paints work is known as contact leaching. The active ingredients in the resin are soluble and packed in such a way that each particle of biocide is in direct contact with another. This means that when one particle dissolves, an adjacent particle becomes exposed to the surrounding water.

There are also products that are considered permanent coatings and may be being promoted as environmentally friendly solutions. They may carry guarantees that the product will last over 5 years or even 10 years. They are generally a more concentrated form of copper based paint and while it may not require such regular maintenance or recoating it does none-the-less use copper as a basis of its paint. Non-toxic coatings are relatively new and are generally applied by a professional. However, these may suit you needs so talk to the manufacturer for more information.

In the past there were soft or traditional paints which have largely been outdated by the newer technologies. The active ingredient within these paints is Cuprous Oxide which is suspended within the paint matrix and allowed to leach out over time, along with the binder, leaving a honeycomb like coating that needed to be removed once every few years. 

Which paint should you use?
You need to consider the following points when selecting the type of paint to use:

• Type of hull substrate: In water copper corrodes aluminium so avoid using copper based paints on aluminium hulls and propellers. Steel and wood hulls should be protected by the relevant primer first.
  
• Type of boat and speed: Over 25 knots self-polishing or erodible paints can be worn away too quickly.
  
• Where you are: In coastal waters antifouling has to combat not only slime and weed but also animals such as barnacles. Fresh water tends to be still or slow flowing, with higher concentrations of organisms and can be subject to lime scale fouling in areas with very hard water.
  
• U.K. or Abroad:  Temperature also has a significant affect on both the fouling present and the way antifouling paints work so whether you in the UK or abroad is important. In addition, there are different national regulations as to the contents of antifouling paint so be sure you are aware of these.
  
• Mooring Situation: Hard antifouling is advised if your boat is moored at a location that dries out each low tide. Antifouling degrades rapidly in air and performance can be affected just a week after being ashore.

Application
Each product has its own guidelines as to quantities required. However, there are a few generic points to remember. 

• Do not dry sand old antifouling, the dust is toxic wet sand only and capture the residue which should be disposed of as hazardous waste
• Underwater primer should be added to bare hulls prior to antifouling
• Hard antifouling leaves a layer of resin which needs to be wet abraded before overcoating 
• Remove any erodible layers and apply a primer layer before applying hard antifouling 
• Apply the correct number of coats and stick with the recommended drying times for each layer 
• Choose a dry day for painting as moisture in the air can affect the bonding properties of the paint. 
• Apply extra layers to areas prone to wear including all leading and trailing edges, the waterline, keel and rudder. 
• Launch as soon as possible, definitely within the recommended time after painting

Maintenance
Care should be taken to remove only the fouling and not the paint itself which is a pollutant and should not enter the water.

Pressure washing and in water scrubbing technologies should only be used as mid-season scrub on hard antifouling where the paint properties remain intact. Any fouling that has accumulated on self-polishing or erodible paints should be removed by sponging or the antifouling itself will be removed. 

Whatever happened to TBT?
Recognition of the widespread environmental affects caused by TBT resulted in the Europe-wide ban of its use in 1987 on boats under 25 metres. Application of TBT antifouling to all ships flying flags of EU countries has now been forbidden since July 2003. Existing TBT coatings will need to be sealed off or removed by July 2008. 

How to find more information
There are a number of supplier s websites that provide useful information. We have also put together an overview of the different antifouling paints available, the A to Z of antifouling which can be downloaded here.