Removing antifouling paint with soda blasting

Applying antifouling paint: step-by-step

When you make the decision to apply antifouling the key to achieving the best result lies in preparation. Have a look at the weather forecast !  From March to May is probably your best bet for perfect weather if you are painting outside. Furthermore, painting at optimum times (mid to late morning and mid-afternoon) helps to avoid affecting drying time and finish. Before buying the antifouling, measure the area of the hull to ensure you purchase enough product. Other preparation involves draping and shielding, taping, sanding, re-taping, dusting, filling, fairing, priming, more sanding, more dusting.

The newer and shinier the hull looks the less of this preparation you will have to do. Ensure that the surface you are going to paint is in good condition with little to no damage and compatible with the antifouling you are applying. The best way to do this is to carefully read the manual and instructions on the can before applying. Then you are ready to paint!

Step 1

Safety first ! Make sure the area you are working in is well ventilated. Wear protective clothing to avoid irritation. A set of goggles, dust mask and gloves goes a long way in protecting yourself from harm.

Step 2

Carefully inspect the boat. Take note of previously painted surfaces, separation or peeling, damages and the state of the vessel. The state of the ship can be divided into three categories

Good condition Start cleaning/brushing the ship before degreasing and sanding
Little damage Remove any growth with a high pressure washer then proceed to the “good condition” steps
Bad condition Remove the existing layer entirely. See below on how to remove antifouling paint

Step 3

Mask off borders. Try to tape as close to the existing bootstripe as possible. Be sure to tape around metal parts as the copper will cause galvanic corrosion as it reacts to the metal. Keep in mind that general purpose tapes are only designed to be left on a surface for a maximum of 24 hours. Any longer and you’ll be setting yourself up for a hefty tape removal job. Consider “long-mask tape”, especially for multiple coats.

Step 4

Apply the paint. Sometimes the heavy ingredients drop to the bottom of the can, so it is advisable to stir a new can of antifouling. Pick the right accessories to match the type of paint. Preferably, use a roller with a solvent-resistant cover to avoid the bottom paint dissolving the applicator as is the case with household-variety rollers. Make sure to follow manufacturer’s instructions on coverage and the optimum number of coats. For soft paints, it is especially important to apply a thick layer. Apply extra coats to the bow, rudder and keel which are high turbulence areas and therefore experience more wear.

Step 5

Let the paint dry. Manufacturers state the recommended curing time in the instructions. If you are applying more than one coat, check the minimum overcoating times (time before you can apply another coat). Additionally, you should take not of how long you can wait before relaunching the boat into water. Trilux 33, for example, has a maximum immersion time of 1 month. If you exceed the times apply a high pressure fresh water wash to the boat before relaunch.

Step 6

Remove the tape and clean up the area. Properly dispose of any old paints and solvents. Hold for a ‘Household Hazardous Waste Collection Day’ or contact your local Council for guidance on disposal. Never pour paints down drains or on the ground.

Removing antifouling paint from your vessel

It’s a dirty job but it needs doing. Whether your coating is old and showing wear and signs of failure or perhaps you have chosen to change your antifouling, these basic steps will help you get your vessel ship-shape and ready to go.

In some cases you will have to completely strip the old layer. For example, if you are switching from hard paint to soft paint. If you notice flakes and blisters as a sign of trapped water in the paint –  removal is imminent. Additionally, a moonscape effect on the surface indicates the need to refurbish the paint.

Most self ablative paint removals require only a high pressure water wash to strip the hull after a season. A hard antifouling paint on the other hand takes a bit more work. Expert removal ensures the best result and minimizes damage to the surface. For this service you can expect to pay approximately NZ$ 50,- per foot.

Top 3 ways to remove antifouling paint



1. Dry scraping

This process involves using a scraper to rub off paint. The method itself costs close to nothing but requires a large amount of labour to do properly. Nevertheless, this is the quickest way to peel away the antifouling. There are three known scrapers for boats namely; triangular, bahco and flat blade. These vary in sharpness with the latter needing to be rounded off at the edges to avoid digging into the paint.

2. Chemical stripping

To lessen the scraping effort, using chemicals to strip the paint is a viable option. However, not any paint stripper will be suitable – the paint will have to be safe for Glass-reinforced plastic (GRP) use. Chemicals work better in warmer weather but can dry out if left overnight. Use cling film to cover applied areas if you are leaving the paint for extended periods. Quik Heavy Duty Brush on Paint stripper is an easy to use chemical stripping agent designed to remove organic paint coatings. A 1 litre can costs approximately NZ$46,-.

3. Soda blasting

If simplicity is your main objective this method ranks as the best in that category. It involves using a soda ‘pot’ and a compressor to blast paint off the hull. The soda explodes on contact with the surface, eating through layers of paint and primer without damaging the GRP. Hard medium can also be added to the soda mix to increase the strength and blast away more than paint. The larger the compressor the quicker the job will be. Acquiring one with a group of fellow boat owners could save you money and time.

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