Anti-Fouling Paint

The first recorded antifouling process was the use of copper plating to sheathe the keel and underwater planking of HMS Alarm in 1761. The copper sheathing was successful in preventing wood-boring worms from damaging the hull, and also prevented the growth of weeds, as the copper produced a oxychloride film when immersed in water. Around 1770, the Royal Navy sheathed the entire fleet! 

Over time, as more iron was used in ship production, copper sheathing became impracticable, due to galvanic corrosion. Relatively ineffective and expensive paints were developed in the late nineteenth century. 

It wasn’t until the 1960’s that the modern version of antifouling was developed: a paint which is self-polishing, and uses seawater’s ability to react with the paint and release antifouling chemicals at a slow and controlled rate. Additionally, the combination of ingredients in modern antifouls prevent any copper present from reacting to other metals present – so galvanic corrosion caused by antifouling is of little concern.

Many breakthroughs have taken place in the last 50 years and today we have many brands, types, chemical compositions and colors to suit every type of boat and boater. 

Lets break down the types available and their uses:

Two major divisions can be seen: Hard and Soft

A hard antifoul gives a solid coat that is smooth, thin and hard to the touch – it needs to be scratched, scraped or sanded to remove. Hard antifouls should be applied just before launch, and are rendered ineffective if the boat is removed and relaunched repeatedly. Hard antifouls typically last one season only. Example: VC17

A soft antifoul looks and acts like a layer of paint, it can be removed with a heavy blast of a power washer, and many brands work well on boats that are trailerable and removed from the water and re-launched during the season. Soft antifouls often last multiple seasons. Example: Micron CSC

A decade ago, it was fairly easy to simplify the difference: Hard antifoul for racing sailboats – boats that want as little drag and as smooth a hull surface as possible. Soft antifouls for trailerable boats (sail and power), larger power boats, and sail-boaters who want multi-season protection at the cost of racing speed.

I would suggest this as a place to start – but recent years have added more elements to the mix, including:

•    Water based paints – marketed as the most environmentally friendly option.

•    Copper or non-copper bases (copper being the traditional base to prevent fouling).

•    Single vs multi-season protection.

•    Color options.

•    Compatibility with other brands or types of antifoul.

•    Hull type – wood, fiberglass, steel, or aluminum.

 

So – How do you choose which antifoul is right for you?

Start - With the type of boat and the way that it’s used: Are you a racer? Cruiser? Does your boat sit at dock more often than not? Freshwater? Salt Water? Is the boat in the water throughout the sailing season or does it come in and out on a trailer or cradle? Is the boat in the water year-round, or is an extended voyage planned?

Next - What type of hull do you have? A bare gelcoat hull will require a layer between the gelcoat and the antifouling (called a ‘barrier coat’, and acts as a primer as provides protection from osmotic blistering). Is there existing antifouling on the hull? If so, some prep work may be in order, or you may choose to apply an antifoul that is designed to go over other types/brands of antifoul. 

Metal hulls (especially aluminum) typically require an epoxy-type primer prior to applying antifoul

Finally - Coverage, cost and color. Some antifouls have larger coverage for the same size of paint can (ie it will cover more boat hull than a competitor), but this may not mean a cost savings overall. Run some comparisons if you’re on a strict budget. Blue, green, red and black are quite common amongst competing brands. 

Pro tip: Paint two coats with two different colors. As the top coat wears off over time, the second coat (in a different color) will be exposed, giving you an easy view of the state of your antifoul when looking at the hull in the off-season.

Antifoul application instructions are dictated by the manufacturer. Each type of antifoul has specific application instructions, including surface preparation, compatibility with other antifouls already on the hull, time of application (sometimes it must be done 12 hours before launch), ambient temperature at the time of application.

If you’re applying antifoul by yourself, be mindful of the safety instructions indicated by the manufacturer. Most of these products are chemical and/or metal based, and exposure can be harmful to humans. Do not breathe fumes or dust, wear a respirator, gloves and eye-protection. 

Many marinas and yacht clubs will not allow hulls with antifoul to be sanded on the premises (due to the toxic nature of the dust, and the ease with which the dust sticks to and damages any fiberglass that it lands on!). Those marinas and clubs that do allow hull sanding require the area to be properly tarped, shielded and cleaned up thoroughly after work. Check with your yard before beginning work.

Now is a great time to begin your research before the spring rush. You may want to take a good look at your hull to determine what it needs to move forward into the next year, and the type/cost and availability of your preferred antifoul. Look at yard regulations, safety and application instructions. If you’re hoping to hire someone to do the work for you, get in touch soon, as bookings fill up fast as warm weather hits.

I encourage you to read and understand the instructions before application – these factors really do matter, and can make the difference between solid protection and a botched job that cracks and peels off the hull.