What is bottom paint? 

Bottom paint is applied below the waterline on your boat, and typically refers to antifouling paint that prevents marine growth from clinging or growing on your boats' hull. This marine growth, which can consist of barnacles and slime, can slow you down and increase your fuel costs because the engine has to work harder to move your boat through the water. A bottom full of barnacles and weeds can also put you in harm’s way because it can seriously hamper your ability to maneuver.

If you are new to boating you may hear terms that don't quite make sense and sometimes embarrassed to ask the simple questions. Don't worry, this is a quick guide to the simple terms used for bottom paint.

Fouling – The growth of marine life (slime, barnacles, muscles etc) underwater on the bottom of the boat (the hull).

Antifouling - Treatment of a boat's hull with a paint or similar substance designed to prevent fouling. All of our bottom paints are antifouling.

Biocide – An agent such as copper, zinc and or Econea added to a paint to stop or slow down the growth of biological life such as barnacles, slime, grass, muscles etc. on the bottom of a boat making the paint antifouling.

Dual Biocide – When two agents are used in an antifouling bottom paint such as copper, zinc and Econea added to a paint to stop or slow down the growth of biological life such as barnacles, slime, grass, muscles etc.

Bottom Paint – Bottom Paint is the paint applied to the bottom of a boat (underwater) with biocide to stop marine growth such as slime, barnacles, grasses, muscles etc. Bottom paint is referred to as antifouling. Most bottom paints use copper (Cuprous Oxide) as the active ingredient or biocide to prevent marine growth. However, there are newer ingredients that work as good or better than copper such as Zinc (Zinc Pyrithione) and Econea. Most of US Marine Products Bottom Paints use copper as the active ingredient. Except for Coastal Reserve 650 which uses Zinc and Econea.

Hard Bottom Paint – Hard bottom paint is exactly as it sounds, hard. Like the paint on your car if you wipe it with your hand it does not come off. Most bottom paint today is ablative, which is a newer technology that has been around for the last 20 years. Before ablative paints all bottom paints were hard. Some people still use hard paints but over time they are becoming less popular. US Marine Products does not make a hard bottom paint. All of our ablative bottom paints will cover hard bottom paints without issue.

Ablative Bottom Paint – Ablative bottom paint has biocide of copper, zinc or Econea, or combination of two being a dual biocide. The major difference is it sheds paint like a bar of soap, wearing away as you use it. This action of ablating occurs as the boat moves through the water wears away the paint every time you use the boat this helps slow down paint build up and also helps the antifouling properties by not allowing anything to stick to the bottom of the boat easily.

Copper Content – As a rule of thumb the higher the percentage of copper in the paint the better the paint works. For example a 45% copper paint should work better than a 25% copper paint. This is usually true however, paints can be made softer allowing copper to release faster. Generally speaking, the more copper content the slower the copper release of the copper over time. The lower the copper content the faster the release of copper this allows a lower copper paint to work as good as a higher copper based paint over the period of time it was designated to release all of its copper.

Copper Free Paint – Copper free paint is paint that does not have copper (Cuprous Oxide) in it. Instead zinc (Zinc Pyrithione) and or Econea is used. The reasons for the use of different biocides is aluminum boats cannot be painted with copper. If copper is used on an aluminum boat it would create much greater electrolysis on the hull of the boat causing the boat to deteriorate due to this. The other reason why copper would not be used is it is harmful to shellfish and in a few areas of the country they do not allow copper to be used on boats.