Technology Focus |
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Antifouling Made Easy |
So the time has come and your pride and joy finally requires a new coat of antifouling paint. As is typical with many facets of our lives these days you can seemingly be overcome by the choice of products available. However, once you apply logic the choices can usually be reduced. Getting to that choice however can be stressful and hopefully this article will help make choosing your antifouling far easier. Types of Antifouling The types of antifouling available can be split into two types, hard and eroding. You will probably find other descriptions such as ablative, polishing or self-polishing. All these descriptions can be put under the umbrella of eroders. The basic and original type of antifouling is the so-called hard antifouling. This is one that when immersed and in a wet state is hard enough to withstand regular wiping down with a cloth, sponge or similar object without removal of substantial quantities of paint. Some local authorities may only allow these types to be used so the decision may have been made for you. 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, after a few seasons, you are left 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 antifouling, as their name suggests, wash/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 and you are a keen racer, International VC Offshore with Teflon might be your choice. VC is specially formulated for racing yachts with its reduced drag qualities bought about by the Teflon finish. The other choice of hard antifouling is International’s Longlife, a high strength copper oxide based product, suitable for all substrates except aluminium, and available in a range of 20 colours. For aluminium substrates International’s Interspeed 2000 is your only choice. Eroding Choices If you have decided you want an eroding antifouling, with substrates other than aluminium, there are several choices. International Micron Extra is a heavy duty product for heavily fouled areas, extended life and suitable for trailed boats, International Micron CSC is a general all round excellent performer and International Coppercoat is the lower cost option still able to give a very good all round performance. For aluminium substrates International Cruiser Superior is the only choice. Surface Preparation and Priming Having decided what antifouling you are going to apply the condition of your hull needs to be considered. Irrespective of which paint is already on your hull, it should be in good condition with little or no damage and be of a compatible type to that which you are going to apply. You will need to give the surface a good wet sand with 80 grit paper. This will remove the top layer of paint that is depleted in biocides, contains salt and calcium deposits and which will also be in an unstable condition unable to accept a new coat of paint. Failure to remove this layer will lead to blistering, delamination or even poor antifouling performance as ingredients and biocides in the new paint permeate back into the old depleted layer. If the paint is an unknown product, after sanding and washing, allow it to dry thoroughly and apply a sealer/tie coat of International Primocon. This will seal the old antifouling off avoiding any unwanted interaction between old and new and will give you a good surface that the new antifouling can bond to. Do not be tempted to apply a coat of Primocon over old unsound antifouling in the hope that it will hold it all together and allow new antifouling to be applied over the top as it won’t, and the antifouling will fall off. If the hull has damaged areas then these will require re-priming either in the original primer that was used or you can use International Primocon. This is an easy to use product, being single pack, fast dry and even uses the same thinners as your antifouling for thinning and cleaning up. The beauty of Primocon when trying to paint damaged areas is that you can simply overlap the primer over surrounding clean and dry antifouling areas, try that with a two pack epoxy and you will have major problems. If your hull is new, then choice of priming is one for the individual. You can use single or two pack. The two-pack International Interprotect epoxy primer will give you a harder, tougher finish and, for gelcoat boats, will offer a degree of osmosis resistance. For a more simple priming system however Primocon is the product of choice. Simply prepare the surface as per the label instructions and apply the required number of coats. Primocon makes future repair work easy as it is easily recoated with itself and any antifouling with minimal hard work. Epoxies usually require a fair degree of sanding and for small touch ups mixing small amounts of a two-pack product with special thinners and cleaners can become a major headache. Antifouling Before purchasing your antifouling, work out the area of your hull to ensure you purchase sufficient product. Insufficient film build of antifouling is the single largest cause of premature failure. The apply all of the antifouling you have. Putting some aside for next year is not a good idea as the product may go off in a part-can. Part-cans may then become a disposal problem. Better to put the paint on your hull than in some waste disposal area. Ensure that you apply the antifouling reasonably evenly, adding only very minor levels of thinners (up to 10%) to help product application. Areas on the hull that you would expect to have greater wear, should have at least an extra coat applied and this includes areas that may have direct sunlight on them such as the first half metre or so down from the waterline and any leading edges such as keel, rudder and propeller 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 so extra coats will not necessarily be required here. Once you have finished painting protect the antifouling from the sun as some ingredients in antifouling paints can oxidise leading to reduced performance when immersed. If after antifouling, your boat it gets to sit on the hard stand for some days in hot weather or direct sunlight, it might be a good idea, prior to launching, to lightly wet sand the surface with 400 grade paper. This will ensure the surface is good and active. 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 hard scrub or light wet sand depending on the type of Antifouling used – scrub hard types and light sand eroding types. Never, dry sand antifouling paints of any type. Health and Safety When handling any of the above-mentioned paints please remember to wear the appropriate safety gear - even when wet washing down old antifouling, care should be taken to avoid splashes in the eye or on the naked skin. |