Antifouling paint performance in general terms is dependent upon the film thickness applied at application time. Interlux antifoulings are formulated to the optimum viscosity, or thickness, for their designed application thickness. Thinning can significantly affect the application properties of an antifouling.
When used for these applications, please follow the manufacturers' guidelines. (typically thin bottom paint no more than 10% unless barewood (20%) per application)). Be sure to use the correct thinner for the bottom paint that you are using. Do not mix competitive brands.
One: Antifoul poisons the waters you boat and fish in
The copper in your paint has a purpose – to stop living creatures from making a home on your boat. That means it can kill or injure them in the wider environment too. Most bottom paints contain copper and all of it eventually leaches into the water.
If the existing antifoul is not in good condition it will need to be scraped back. If you do not remove this antifoul you risk the new coat of paint peeling off. There might only be a few places that you need to scrape off.
The instructions on the tin will tell you - it's usually 6-12 weeks, unless it's hard antifouling, in which case freshening it it with a light sand may do the job.
Complete a high pressure fresh water wash to remove loose antifouling. Ensure all residue and wash water is contained and disposed of according to local legislation.
There isn't a definitive answer to how often you should antifoul your boat as there are many variables at play, but as a rule-of-thumb, we suggest you antifoul your boat at least once a year.
Thinning your antifouling product can be useful in hot or cold temperatures if its flow properties are no longer as they were. Diluting antifouling can also be advantageous in extremely windy weather or when applying a top coat.
Here's how antifouling benefits your boat: Prevents Marine Growth: The biocides in antifouling paint actively repel marine organisms, stopping them from forming colonies on the hull. Without this layer of protection, marine growth can quickly accumulate, causing drag and slowing your boat down.
Applying a primer is a must for bare surfaces and will also help the antifoul will properly stick to the hull. Many primers contain technology that enables multiple coats to be applied in just one day. Furthermore, primers including Hempel's Underwater Primer can also be used a sealing between old and new antifoul.
If you plan to store your boat in any aquatic environment, you will need to apply antifouling paint. By leaving your boat in the water with no protection, you are letting marine life grow and attach to your boat, increasing your boat's fuel consumption and slowing the boat down on the water.
The ultrasonic system and sound waves are easily able to protect the hull from marine fouling but the systems can struggle to completely prevent fouling growth from occurring at the waterline.
Copper is an effective and safe antifouling active ingredient and the use of copper has allowed the effective removal of tributyltin (TBT) from the market and from the environment as required by International Maritime Organisation (IMO) Treaty, which fully entered into force in September 2008.
To really speed up the process, it is also possible to spray antifouling paint onto the hull. However, due to the toxicity of antifouling, this should only be undertaken by professionals with specialist facilities designed for this type of work.
The process of bottom painting can be messy and costly to do every year. It requires sanding down the boat's bottom and repainting with new antifouling paint to continue protection. But luckily if you use multi-season paint you can get away with a touch up for a year or two.
Smooth films are an alternative to antifouling paint for protecting boat hulls. This technique involves applying a silicone adhesive film to the hull surface. The lack of adherence prevents marine organisms from binding to it.
Typically, 2-3 coats are required for one season of use. However, if your existing antifouling is in good condition, a touch-up may be suffice. Also, some antifoulings, including Seajet Coastal 037 Antifoul and Hempel Tiger Xtra Antifoul only require one coat for a whole season.
How often you use your boat can impact the lifespan of the antifouling used. Antifoul on boats used regularly will last around 10-12 months, however, if your boat isn't used for extended periods and is sat on a mooring this will reduce to around 8-10 months before the hull becomes excessively fouled.
Most antifoul paint is required to be applied 125microns -150microns wet or 75-80 microns dry film thickness (DFT) per coat to deliver a life expectancy of about 12 months. RPAYC lays two coats by roller, each 125-150 microns over a vessel in two passes. We lay a 3rd coat around the waterline and leading edges.
If your existing antifouling is in poor condition, we strongly recommend removing it completely before repainting.
Lightly wet-sanding the surface with 60 or 80 grit wet-and-dry paper wrapped over a sanding block will provide a key and help the antifoul to adhere well.
If left unattended, fouling leads to corrosion of the hull and to the vessel's deterioration. In high growth areas, it is common to hire divers to scrub the bottom of your boat every few weeks, even though you may have toxic antifouling paint on the bottom. Fouling begins with the attachment of bacteria.