DIY Antifouling

Aug 25, 2021 | Antifouling Tips

Why antifoul your boat?

Antifoul is a specialist paint applied to the hull of your boat. Antifouling your boat will help to prevent the growth and build up of organisms such as barnacles, mussels, algae and other marine foul on the hull. There are many benefits to antifouling your boat; it improves fuel efficiency – reducing fuel consumption, hull performance, reduces damage to the hull and improves speed as well as helping prevent the spread of non-native species. You can read more about the benefits of antifouling in our blog, do I need to antifoul my boat?

Antifoul paints contain a mixture of organic and inorganic compounds that work as biocides (pesticides) to kill off any marine life that tries to attach to the hull of your boat.

Antifouling a boat can be hard work for boat owners so we’ve put together this guide on how to antifoul your boat to make the job as straightforward as possible, including the type of antifoul to use, how to apply it and the safety precautions you’ll need to take.

Which type of antifoul will I need for my boat?

There are two main types of DIY antifoul paint available, hard (also known as self-polishing) and erodible (also known as ablative).

A harder, self-polishing antifoul paint is suitable for high speed boats whereas erodible or ablative antifoul is used on boats that don’t regularly exceed 30 knots – perfect for pleasure boats, yachts and fishing boats.

There are other types of antifouling paints and layers available but these are often only professionally applied as they are more toxic than the more readily-available antifoul paints or more suitable for professional racing boats and are much less cost-effective.

Furthermore, which antifouling you need may depend on the material of the hull (e.g. aluminium hulls need a different formulation to other hull types) and where you plan to use your boat. Different waters have different levels of fouling and some areas have restrictions on the types of antifouling they allow in their waters, as antifouling contains biocides certain types are restricted from use around coral reefs and other marine life dense areas. The leeching of the paint toxins into the water can lead to an accumulation within the food chain, having a damaging impact on the environment, so be sure to use the least toxic paint possible that still meets your needs.

Steps to antifoul your boat

1. Get your boat out of the water

Your boat will need to be out of the water so your first task is to ensure it is somewhere dry and protected from the elements if applying the paint in inclement weather.

You may also have to raise your boat off its trailer in order to have access to the whole hull so bear this in mind.

2. Clean and prepare the hull

First of all you will need to clean the hull down using a pressure washer to rid it of any sea salt, loosely attached dirt and grime.

Secondly, scrape the hull down to remove any barnacles or other organisms and debris that may have attached to the hull whilst your boat has been in the water.

Finally you need to sand down the previous layer of antifouling slightly to ensure the new coat will stick, a process known as keying. Use a wet sanding method in order to comply with the British Coatings Federation safe antifouling initiative. Before doing so, place a tarpaulin down to collect and easily dispose of the sanding debris.

Rinse down the hull after sanding to create a clean surface on which to paint and, when dry, mask off the areas to which you are applying the paint and be sure to cover any fixtures and fittings on the hull that cannot be removed.

3. Check whether you need a primer coat

If you’ve recently bought a second hand boat and are unsure of the make of antifoul already on the hull then it may be best to apply a primer or full barrier coat. Alternatively, you must be sure to remove all existing antifoul as not all antifoul paints can be overcoated.

4. Applying the antifoul paint

Ensure you have selected the correct antifouling paint for your boat and the area in which you will be using it. If unsure, ask a local chandler for advice. Prepare the paint by allowing it to come to room temperature and then mixing thoroughly for 10 minutes to ensure an even consistency, like we said, this isn’t a quick process so don’t rush this stage.

You will need to apply multiple coats of the antifouling paint to the hull in order to maintain optimum hull performance and fuel efficiency, you can do this with 4″ rollers or a paintbrush, loaded generously. Check the coverage rate per litre of the paint on the back of the tin to ensure you buy enough to complete the job.

Thickness is important. An easy-to-remember rule is two antifouling coats on the whole hull and three in high traffic areas such as the rudders and waterline. You may wish to use a wet film thickness gauge to ensure the perfect antifouling paint thickness, these are readily available in DIY stores or online. Leave the antifouling to dry completely between coats.

5. Clean up and prepare your boat to launch

Remove the masking tape, coverings for any fixtures and fittings and carefully clean up and dispose of any antifoul waste after reading our precautions below.

What precautions do I need to take?

Both the paint and the dust from antifoul is hazardous, as is any contaminated water, so it is important to work safely with any antifouling products to protect yourself, others around you and the environment. Guidance from the British coatings federation suggests a few easy safety measures when using antifoul paint in their safe antifouling initiative.

The dust and leftover paint are classed as hazardous waste so you will need to dispose of them carefully and correctly, in line with local authorities. You can read more about the legal requirements for antifoul disposal via The Green Blue website.

Importantly, ensure you are wearing adequate personal protective equipment including a mask, disposable gloves and goggles when sanding down old antifoul and applying the new coats. A respirator-style mask is preferable to a general purpose dust mask.

Is there an easier and greener option for antifouling my boat?

Absolutely! Antifouling is an annual maintenance procedure that many boat owners dread but our electronic antifouling products aren’t harmful to aquatic life and don’t require the yearly workload as traditional antifouling. Instead, ultrasonic signals are emitted to deter organisms from attaching to the hull, providing ultimate non-toxic protection and performance. Read more about our ultrasonic antifouling systems here.