The types of antifouling available can be split into two types, hard and eroding. You will probably find other descriptions such asablative, polishing or self-polishing. All these descriptions can be put under the umbrella of eroders. The basic and original type of antifouling is the hard antifouling. When immersed and in a wet state this antifouling is hard enough to withstand regular wiping down with a cloth or sponge without removal of substantial quantities of paint.

Hard antifouling does not wear away much at all, although abrasive material in the water such as silt and sand may lead to a very minor reduction in film build. Eventually however, you are left after a few seasons with a build up of product that requires removal. The product becomes unsound and does not retain sufficient internal strength to be able to hold together when new product is applied to it. If you have a seriously fast boat or a fast boat that is used very regularly then hard is probably the best way to go. Boats moored in fresh water normally use these types, as the eroding types may not erode very well. Keen racing types sometimes prefer hard products as they can be wet sanded to a smooth finish prior to racing.

Eroding antifoulings, as their name suggests, wear away leaving eventually no antifouling on your hull. In theory, whilst there is antifouling on your hull it will give a degree of protection. With the current generation of paints however this does not happen because as the paint film starts to get thin, the biocides are preferentially washed out leaving paint that is essentially not antifouling paint. This is the time to apply new product.

Hard Choices

If you have decided that a hard type is your best option, International’s Longlife might be your choice, a high strength copper oxide based product, suitable for all substrates except aluminium.

For aluminium substrates International’s Trilux 33 is your best choice. Trilux is specifically developed for use on aluminum boats, outdrives and outboards.

Eroding Choices

If you have decided you want an eroding antifouling there are several choices for substrates other than aluminium. International Micron 66 is the ultimate in antifouling performance even in the harshest fouling conditions. International Coppercoat is the lower cost option still able to give a very good all round performance.

Important Notes

Copper oxide based antifoulings may be applied to hulls made of any material except aluminium. For steel hull, if not overcoating an existing antifouling, the International primer is nesessary.

Most International antifoulings may be applied over most previously coated antifoulings directly, after a light wet sand, washing with water and allowing to dry. Overcoating of some may require a barrier coat of Primocon and other may require removal first.

Antifouling performance in general terms is dependent upon the film thickness applied at application time. International antifoulings are formulated to the optimum viscosity, or thickness. Thinning can significantly affect the application properties of an antifouling, and is therefore not recommended. Insufficient film build of antifouling is the largest cause of premature failure.

Areas on the hull that you would expect to have greater wear should have at least an extra coat applied, this includes areas that may get direct sunlight, such as the first half metre or so down from the waterline and any leading edges such as keel, rudder & prop wash areas.

Grassy growth and slime just love sunlight and are the most difficult species to ward off, so extra paint will help keep these obnoxious species away. Areas under the hull in the dark will generally not attract fouling species so readily and extra coats will not necessarily be required here.

It is a fact of life that when you launch your boat, the antifouling will not start working straight away. It will take some hours for it to come to equilibrium with its surroundings. Meanwhile, floating around in the water are millions of small fouling species on the lookout for a clean surface to colonise and if you are unlucky enough to place your boat directly in a patch of such activity, the result can be premature fouling. This problem can only be resolved by giving the surface a good scrub or light wet sand depending on the type of antifouling used - scrub hard types and light sand eroding types.

Another important point to remember is that the true colour of the antifouling will develop about 4 weeks after immersion.

Why AntiFoul ?

This is a good question. Ever since man decided to play on the water in marine vessels there has been an ongoing battle with Marine Bio-Fouling. This is the build up of marine growth on the hull of a vessel that causes everything from corrosion, loss of speed by increased drag, reduced steering and maneuverability and increased fuel consumption. All things we would rather avoid when motoring. A good quality Antifoul coating will hinder the marine organisms ability to grow on the surface of the boats hull, ensuring the hull remains contaminate free for un hindered use for as long as possible.

Barnicle Organic Growth on Hull Demonstrates the requirement to AntiFoul your Vessel.

What Anodes ?

This is another good question. Many boat owners will be familiar with galvanic corrosion and the costly nature of attending to the issues associated with metals in water. All metals will corrode when exposed to oxygen and moisture and revert back to the basic natural state of their raw material. Without preventative measures and proper maintenance, corrosion can occur very quickly and be costly. However, there are simple measures which can be taken to significantly reduce the effects of corrosion in terms of time and cost.

Metals are graded in 'The Galvanic Series of Metals', reflecting the ease at which they corrode. Softer metals corrode at a higher rate than harder metals. Sea-water is a great electrical conductor and can be a major contributor to the rate of corrosion.

Anode selection should consider the environment, the type of water and the type of vessel. For example, extruded anodes should be used in saltwater to protect non-metallic hull vessels, zinc anodes to protect metallic hull vessels, softer cast sacrificial anodes vessels in fresh water environments, aluminium alloy anodes near a river source and further upriver, and magnesium anodes in environments where there are numerous dissolved minerals, for example a clay water bed or fresh water.

In warm water a harder sacrificial anode is appropriate, in cold saltwater more sacrificial anode surface area is required to achieve adequate protection.
The flow rate of the water will also affect the consumption rate of sacrificial anodes. Soft cast sacrificial anodes will be consumed by water erosion and may not achieve the required protection levels for the expected lifetime. Additional anodes or a harder, extruded sacrificial anode will be required in areas of higher water flow rates.

The briefly described scenarios highlight the importance of considering the environment that the vessel resides in to achieve the greatest efficiency and performance of a sacrificial anode.

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