Whether you have a small boat or a big boat, painting the boat appropriately will look nicer and keeps the slime, barnacles, and other marine growth away. But what are boats painted with? Do they use different paints than normal ones or the same?
Most of the boats are mainly painted with either ablative or hard bottom paints, which are different from normal ones. To tackle various conditions well, they are also painted with varying biocide (mostly copper) levels in it, namely vinyl paints, copolymer ablative paints, copper-free paints, etc.
The normal paints we use don’t contain any harmful biocides like copper, zinc, etc., in it. The anti-fouling paint or bottom paint contains harmful biocides like copper, zinc, etc., to prevent any growth (slime, barnacles, weeds, etc.) on the boat’s hull. But, above the waterline, you can use normal paints other than the paints with biocides.
All those bottom paints contain different levels of biocides (mainly cuprous oxide or other copper compounds) in it, which leaches out over time, stopping the growth (slime, algae, barnacles, weeds, etc.) on the boat’s hull. Hard bottom paint contains more percentage of copper in it than ablative paints.
Nowadays, paints in the market contain 20% to 70% copper in it. The smallest percentage of copper indicates sloughing bottom paints; a little more indicates ablative bottom paints. The largest percentage of copper in the paint indicates it is hard bottom paints.
Related post – Check my article on Why do boats need bottom paint to know the needs and what boats need bottom paints in a detailed way.
Check this video by west marine to understand the basics of the bottom paints or anti-fouling paints well in less than 10 minutes.
Types of bottom paints (anti-fouling paints) and their uses
We will now quickly see several bottom paint types and their uses.
Broadly there are two types of bottom paints for boats, i.e., ablative and hard bottom paints. With varying chemical (biocide) levels in it, there are several other types, namely vinyl paints, copolymer ablative paints, copper-free paints, sloughing paints, etc., to tackle various conditions well.
| Bottom or anti-fouling Paint | Used for | Not used for |
| Ablative bottom paint (aka self-polishing bottom paint) | Boats that are taken on and off from the water or if you use your boat frequently. | Boats that are kept in the water for longer periods without any movements. |
| Hard bottom paint (aka hard modified epoxy paint) | Boats that are kept in the water for a long time without any or very slight movement due to current or tides. | Boats that are taken on and off from the water. |
| Water-based bottom paint (aka copper-free paint) | In the areas that restrict the use of solvent and copper-based bottom paints. | It can be used on all the boats as well, but it will not last longer than other paints. |
| Copolymer ablative bottom paint | Boats that are kept out of the water for longer periods (like winter). | It can be used on all the boats as well. |
| Vinyl bottom paints | Best for high speeds or racing boats. | It can be used on all the boats as well, but not on non-vinyl paints. |
| Aluminum Safe Bottom Paints | For aluminum boats and on aluminum parts of the boats (trim tabs, outboards, etc.). | N/A |
Those are the common bottom paints you may find; still, there are many bottom paints available out there, but those are the major ones to choose from. We will now see each of those paints uses in a detailed way.
1. What are ablative bottom paints used for?
Ablative bottom paints are used on the boats that often go in the waters, not on the boats kept in the water for long times. If the boat moves in the water, these paints start slowly wearing off, releasing copper to stop growth, exposing the hull to new, un-oxidized paint; otherwise, they don’t work.
Soft or ablative or sloughing bottom paints wear off slowly in the water from the hull, releasing a copper or zinc-based biocide, stopping the growth on the boat’s hull—this wearing off rate increases with movement of water. The wearing away of the bottom paint allows for new, un-oxidized paint to be exposed.
For most ablative paints to work effectively, motion is required, so this paint is best if you use your boat fairly often–at least once a week. Otherwise, if the boat isn’t used for a long time, the paint will not wear off, and the new, un-oxidized paint will not be exposed, which can start the growth.
Ablative paints are also good for the boats that are often taken in and out of the water (while trailering). So, if you don’t take the boat out of the water or don’t use the boat quite often (once every 2 or 3 weeks), better stay away from this paint and go for hard bottom paints.
2. What are hard bottom paints used for?
Hard bottom paints are used on the boats that are kept in the water for longer periods of time without moving at all, or there is little movement of water due to currents or tides around the boat, and not used on the boats that are often taken in and out the waters.
The hard bottom paint or hard modified epoxy bottom paint will not wear off like ablative paints. These paints create a porous film on the surface in which the biocides are held in the pores and released slowly to stop the growth on the hull. And these paints last longer than ablative paints.
Since the hard bottom paint will not wear off like ablative or soft paint, so the hard bottom paint is generally used on the boats that sit in the water for long periods of time without moving at all, or there is little movement of water (current/ tide) around the boat.
If you keep the boat out of the water, then after 72 hours, the hard bottom paint will oxidize on the outer surface from the air and becomes ineffective. So, if you take the boat in and out of the water (trailer it), better stay away from hard bottom paints and go for ablative bottom paints.
Related post – Check my article on How long can you leave a boat in the water to know how long can you leave in different waters like freshwaters and saltwater, along with growth prevention tips.
3. What are water-based or copper-free bottom paints are used for?
Water-based bottom paints or copper-free bottom paints are used in the areas where there is a restriction of using solvent and copper-based bottom paints. So, if you boat in those areas, better be using water-based/copper-free bottom paints to avoid any problems in the future.
In some marinas or lakes, they restrict the boats to use the bottom paints that release copper because copper will harm aquatic life in the water. Since the paint will be releasing copper over time, copper may affect the aquatic life in the water.
By the end of the day, all the copper from the paint on the boat’s hull will be leached out. This leaching happens at an estimated rate of two pounds of copper per year for a 30-foot boat. Now, imagine a marina or lake with 100’s of vessels, which can cause problems to the aquatic life in the water.
If there are 100 boats (each of 30-foot in length) in the marine and every boat will release 2 pounds of copper into the water in a year, and all the boats combined will release 200 pounds of copper into the water in a year, which can be a serious threat to aquatic life in the water.
4. What are copolymer ablative bottom paints used for?
Copolymer ablative bottom paints are used on the boats that are kept out of the water for longer periods (winter) because the paint won’t lose its effectiveness when exposed to air for longer periods. So, if you don’t want to repaint the boat every spring, better be using copolymer ablative paints.
When the copolymer ablative paints are exposed to the air for longer periods of time, the paint will not oxidize the outer surface from the air and don’t lose its effectiveness. Simply washing after that long period of storage (like winter) is enough, and you are ready to go.
So, if you haul out your boat after every winter and don’t want to repaint it every spring, you might (think of) go for ablative copolymer bottom paint for better results.
5. What are vinyl bottom paints used for?
Vinyl bottom paints are used on the boats that seek more speed or performance, like racing boats, powerboats, sailboats, etc., because these paints dry to an extremely hard, durable finish that’s tough enough to be burnished smooth, making them ideal for high speeds (boats).
If you like to go fast in a boat or using your boat for racing purposes, then you have to look at this paint. These paints give a very smooth (polished) finish on the hull due to that the water will slide over the hull smoothly without any disturbances, giving the best outcome (speed) out of it.
These paints can also be used on the boats that are kept in and out of the water. They work like hard bottom paints in that they do not wear away, but the biocide is still designed to leach out.
6. What are aluminum safe bottom paints used for?
Aluminum safe bottom paints are used, especially for aluminum hulls like pontoon tubes, aluminum boats, aluminum parts on boats, etc. Because if you use bottom paints containing copper on an aluminum boat, it will attack the aluminum and can cause expensive repairs.
If you have an aluminum boat or aluminum sterndrives or outboards, better be using aluminum safe paints over them because these paints contain copper thiocyanate or zinc omadine as a biocide, so it will be compatible enough to stop any problems on the aluminum parts.
Related post – Check my article on What are barnacles on boats? to know why they attach themselves to boats and how to prevent them easily in a detailed way.
What boats need bottom paint?
Boats that are kept in the water for long periods or used frequently (3 or 4 times a week) need bottom paints because algae, barnacles, weeds start growing on the hulls easily if the boat stays in contact with the water for long periods or frequently.
If you trailer the boat after every ride, then spending 10 or 15 minutes washing and cleaning the boat properly after every ride will be enough, and you may don’t even need any bottom paint at all. Since cleaning and washing will remove all the growth on the hull.
Cleaning and washing the boat after every ride will definitely prevent the growth on the hull, eliminating the growth at the early stages. So, you don’t have to paint your boat at all if you spend some time washing and cleaning the boat (hull) after every ride.
Effects of using anti-fouling paint or bottom paint
There are some effects of using bottom paint or anti-fouling paint on the boat. Here are some effects of using anti-fouling paint or bottom paint for a boat (source).
- Leaching off anti-fouling paint or bottom paint from the boat’s hull can harm aquatic life.
- Thick layers of anti-fouling paint may increase your boat’s weight, and eventually, it may increase your gas consumption as well.
- You need to do extra maintenance to the boat’s hull, and sometimes DIY can be dangerous.
Those are the primary concerns about the bottom painting your boat with anti-fouling paint. So, think about those problems before painting your boat bottom unnecessarily.
1. Anti-fouling paint or bottom paint on a boat may harm aquatic life
Bottom paint or anti-fouling paint, which is painted on the boat’s hull, will release (leaches) copper over time to reduce the growth of algae, barnacles, or any micro-organisms. Since the paint is releasing copper over time, copper will affect the aquatic life in the water.
Most bottom paints contain copper, and by the end of the day, all the copper from the paint will be leached out. This leaching happens at an estimated rate of two pounds of copper per year for a 30-foot boat. Now, imagine a marina with 100’s of vessels, which can cause problems to the aquatic life in the water.
If there are 100 boats (each of 30-foot in length) in the marine and every boat will release 2 pounds of copper into the water in a year, and all the boats combined will release 200 pounds of copper into the water in a year, which will cause damage to the aquatic life.
2. Thick layers of anti-fouling paint may increase your boat’s weight, and eventually, it may increase your gas consumption as well
Although it may sound weird (how the paint will increase the boat weight), yes, it increases your boat weight.
If you are painting the boat’s hull each year, and while repainting, if you didn’t scrub the hull well, then those thick layers may eventually increase the boat weight. Although there won’t be any significant increase in weight, there will be some difference if the boat size increases.
There will be only a less increase in weight, not a significant difference. For a 30 feet boat, it will take around 1 – 2 gallons of paint for two coatings. Like that, if you do it 3, or 4 times and if you didn’t scrub the boat properly before repainting it, then it may increase 50 pounds (roughly) weight overall for 3 or 4 times.
Again, if the boat’s weight increases, then the boat displaces more space in the water, then the boat requires more power, and it takes some time to push that extra water out of its way. So, the gas consumption of the boat increases if the weight of the boat increases.
3. You need to do extra maintenance to the boat hull, and sometimes DIY may be dangerous
Bottom painting a boat is not a simple task, it consumes your time if you are doing it yourself, and it consumes more money if you are giving that job to others (boatyards).
Painting is one work; after that maintaining it and repainting it is another work. While repainting the boat, you need to scrap the hull to remove the old paint. This whole process is a cyclic process. Once if you apply the paint, over time, the paint wears off, and again you need to repaint the boat.
Once the paint wears off, again, you need to repaint it; otherwise, algae, barnacles, or micro-organisms may start growing, and it may not look good on the boat—every time you need to spend money on it. Again, if you decided to give the job to the boatyards, then it may become expensive.
Nowadays, many states are banning boat owners from DIY bottom painting jobs, and many boatyards are also not accepting it to a DIY job due to the risk factors involved in it. Giving the painting work to boatyards means it takes more money and expensive.
Overall, maintenance is a big problem, and it is expensive as well. Painting the boat by yourself is dangerous as well. So, you need to do extra maintenance to the boat hull, and sometimes DIY may be hazardous if you don’t know how to do it properly.
The takeaway
Most of the boats are painted with either ablative or hard bottom paints, and boats are also painted by mixing the chemicals (biocide) in different proportions to the paint, namely vinyl paints, copper-free paints, aluminum safe, copolymer paints, etc., to tackle different conditions well.
These anti-fouling paints (bottom paints) release biocides (mostly copper, some other paints will have other biocides) to prevent growth (slime, algae, barnacles, weeds, etc.) on the boat’s hull. Since it leaches out the copper (other biocides) into the water, it creates a threat to aquatic life.