Anti-fouling paint is a type of underwater hull paint, also known as bottom paint. These specialized coatings are designed for the exterior of the hull of a ship or boat, and combat the growth, as wells as, the detachment of underwater organisms, such as seaweed, algae and barnacles. These aquatic life forms bind to the hull and impact a vessel’s performance and longevity.
Anti-fouling paints are often applied as one component of a multi-layering process which can have other benefits in addition to their antifouling properties, such as acting as a barrier against corrosion on metal hulls that will degrade and weaken the metal, or to improve the flow of water past the hull of a boat or yacht.
Boaters recognized early on it is important to keep the bottom of their craft free of barnacles due to loss of speed and performance. The key is knowing when to pull your boat out of the water for a new bottom paint application. Ablative paints are typically reapplied every 1–3 years. One way to ensure you reapply your ablative antifouling paint when it’s needed is by adding a signal coat or flag coat.
To apply a signal/flag coat, when you are getting multiple coats of ablative bottom paint applied to your hull, make the first coat a different color. For example, if the bottom is going to be painted blue, make the first coat red. When the blue paint wears off and you see the red flag coat, it is time to repaint.
If you need further assistance with your boat painting project feel free to contact our technical team Monday-Friday 8:30-5:00 pm EST.
Antifouling bottom paint is needed if you store your boat in the water. If left in the water without protection, marine growth may attach to your boat’s exposed hull. Marine growth slows a boat down and increases fuel consumption. Here are the items that you will need in addition to the bottom paint for the proper anti-fouling bottom paint application.
• 60–100 grit – Suitable for the removal of paint or to sand gel coat prior to the application of antifouling paint.
• After sanding remove sanding residue by wiping with a cloth that has been dampened with the proper solvent.
• Masking Tape– When it is necessary to mask off areas use a high quality clean edge masking tape, especially when the masking tape will be left on the surface for a long time.
• Brushes– For antifouling paints use a natural bristle brush but not necessarily one of as good quality as you would use to apply topside finishes.
• Rollers – Most solvent resistant rollers will have a phenolic core and will say that they are for use with oil based paints or epoxies. For antifouling paint and epoxy primers, use a 3/8”-1/2” nap roller
For convenience, you can find most needed supplies in ourPaint Application Kit.
Most Antifouling Bottom Paint is marketed toward the harsh conditions of the Caribbean. But which Antifouling Bottom Paint will work best in Freshwater Lakes?
The short answer is this: Antifouling Bottom Paint that works well in the harsh conditions of the Caribbean will be more than enough protection for boats in freshwater lakes. The real trick is choosing the paint that will fit your situation the best. Choosing a bottom paint with more biocide (usually cuprous oxide) will be more potent and fight off growth more successfully. Sometimes you don’t need to purchase the strongest and the greatest. A paint with just the right amount of biocide will do nicely and can also save a few bucks.
Here are some basic guidelines to help you decide which paint is best for your boat.
If the boat comes out of the water periodically, such as on a lift or trailer,Ablative Bottom Paintis the correct choice. When in fresh water, slime and algae tend to be the most concerning. Sea Hawk’s AF-33 or Talonand Blue Water Marine’sCopper Shield 25 perform really well with these conditions, especially with the manufacturers boosters added, see below.
If the boat never comes out of the water except to be repainted, a Hard Epoxy Bottom Paintwill keep away the algae. Sea Hawk Sharkskinis a mid strength Hard Bottom Paint that fits a tighter budget.
What about Bottom Paint Additives?
Sea Hawk bottom paint produces a paint additive called Bio Cop TFto help fight against algae and soft growth. This product will boost the effectiveness of your paint’s ability to keep the hull free of growth. **NOTE: Biocop TF Pint may only be used as a bottom paint additive in the following products: AF-33, Cukote, Sharkskin, Talon, and Tropikote. A booster has restrictions to paint added to and you should stick with the same manufacturer.
If you still aren’t sure what is needed for your boat, check out these other How To Articles:
Typically when people discuss bottom paint on a boat they are referring to Antifouling paint. Bottom paint prevents growth of organisms that attach to the hull and can affect a vessels speed, performance, and durability when boat is kept in the water for extended periods of time. If you don’t have that problem, you may not need bottom paint. Antifouling bottom paint typically has a flat, dull finish that is used below the waterline.
If you don’t have a growth problem or would like a nice shine to your boat’s bottom look to our other items like gelcoator a topside paint for moderate water exposure or an aluminum paint with no antifouling agents. Gelcoat adheres to most gelcoats or fiberglass/resins, see how to apply gelcoat. A boat bottom with antifouling will need to have it removed via sanding, sandblasting or bottom paint removerbefore a different type of paint will adhere.
There are generally two types of bottom paint both of which have several variations that create a multitude of products in the market place. The two different types or categories of bottom paint include hard bottom paintand ablative bottom paint.
Hard bottom paint is bottom paint that is a hard modified epoxy. After you apply hard bottom paint it is very durable and does not wear off.Hard bottompaints typically have a higher ratio of pesticides (usually copper) in them that are exposed in the outer surface of the bottom paint coating. As time goes by, the coating oxidizes and becomes less effective in combating marine growth. Hard bottom paint is generally used on boats when the boat sits for long periods of time without moving at all, or there is little movement of water (current/ tide) around the boat. You should not use a hard paint if you boat comes out of the water such as on a trailer or a lift. After 72 hours, the hard bottom paint will oxidize on the outer surface from the air and becomes ineffective. If you are trailering your boat, or keep it on a lift you should always use ablative bottom paint.
Ablative bottom paint, also known as self- polishing bottom paint, is softer and allows the coating to wear off at a controlled rate. Much like a bar of soap, once the boat moves in the water or there is a current and or tide, the outer layer slowly wears away. The wearing away of the self-polishing bottom paint allows for new, unoxidized paint to be exposed. Therefore, if you are trailering your boat, or it comes in and out of the water for any reason, the paint will oxidize within 72 hours. However, once placed back in service, that oxidized ablative paint wears away and exposes a new fresh outer coating with active protection. Ablative bottom paint is a newer technology then hard paint. It is the preferred bottom paint of most users since it typically lasts longer and continuously exposes a new active outer coating that protects against marine growth.
How long does bottom paint last on a boat?
In general, you should apply boat bottom paint once a year, however; some bottom paints can last for two years. If your boat is kept in the water or you use it regularly, you you have it checked annually to determine if it requires a new bottom paint coating.
The cost to paint the bottom of your boat depends on a number of factors including the size of your boat, the paint you choose and whether you use a primer or not. Other factors include whether you will paint your boat or hire someone to paint it. For example, Biocop TF by Sea Hawk, is a popular bottom paint and currently costs $269.77 a gallon and provides theoretical coverage of 315 square feet per gallon. If the bottom surface of your boat is 700 square feet you would theoretically need to purchase three gallons (Biocop is not offered in quarts) at a total cost of $809. 31 for the three gallons.
That may seem expensive for paint however boat bottom paint uses antifouling properties in order to protect the boats bottom from organisms found in saltwater and other elements.
For information on calculating how much paint you need to paint your boat bottom you can refer to our Bottom Paint Calculator.
The best bottom paint that money can buy may NOT be the most expensive. You should buy the bottom paint that works best in your area. That will depend on the temperature of the water, tide changes, the nutrients in the water that feed unwanted growth, and many other factors.
The best bottom paint for you will be the bottom paint that stops the growth and does not break your wallet. If you buy the best performing bottom for the harshest fouling conditions and the warmest waters you would need Sea Hawk Paints Biocop TF or another Top Performing Bottom Paint. This provides you the absolute maximum protection against hard and soft growth on the bottom of your boat. This solution is recommended for high growth areas, or if you are trying to goes as long as you possibly can between bottom jobs. If you are in cooler climates or lower fouling conditions you would NOT need to spend the extra money on Sea Hawk Biocop TF. A better choice that is less expensive and will work in these conditions is Sea Hawk AF-33or the equivalent.
ALUMINUM BOATS: The best bottom paint for an aluminum boat or pontoons is a copper free bottom paint. You cannot put the paints mentioned above (Copper-Based) on aluminum because they contain copper and will react like a battery causing pitting (holes) on aluminum. Therefore, we recommend an Aluminum Safe Bottom Paint. A good choice for aluminum is Sea Hawk Colorkote, it is copper free triple biocide paint safe for aluminum. If the aluminum has never been painted the best practice is to prime with high build epoxy primer like Sea Hawk Tuff Stuffto insure good adhesion and protect against corrosion. If you are painting a pontoon boat for the first time – try our Pontoon Bottom Paint Kit.
The best bottom paint for the outdrives is to brush on Smart Solution. (pint size). If your outdrive has never been painted before, you can use Barnacle Blocker Primer for priming the area application of bottom paint. A great value for this is the Premium Outdrive Bottom Paint Kit. If there is already a bottom paint on your running gear, just scuff sand and paint! Another option is to try an aerosol spray bottom paint. These are easy to apply.
For outdrives a foul release agent may be the choice for you, see here.