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Bottom Painting

 Two Types of Painting

A bottom in good condition, but visible
growth indicates the biocide is exhausted.

The nautical arena involves a lot of painting because the sea, the sun, and the sand take a toll on everything they touch. In fact, we do more painting than anything else. There are two distinct types of painting, bottom painting and topside painting. They serve two very different purposes.

We paint hull bottoms to preserve them from salt and marine organisms.

 Bottom Painting

A bottom prepared for a new coating.

When a vessel is in the water for a period of time, marine life will grow on the underwater surface (the vessel's bottom). To discourage this, the bottom is painted with an antifouling bottom paint. Antifouling paints contain a biocide that slowly leaches from the paint to prevent marine life from attaching to the painted surface. The painted surface is toxic to clinging organisms.

There are different types of antifouling paints for different environments. Some work better in fresh water, others in salt water. Some are more effective in warm water, others in cold water. We can provide the correct antifouling paint for your environment.

 Compatibility with Aluminum

Closeup of an aluminum pontoon with
an antifouling coating.

Most biocides are copper-based and you may have heard that they are incompatible with aluminum hulls. Generally, the combination of copper and aluminum produces an electrolytic reaction that is destructive to the aluminum. Many antifouling paints indeed will corrode an aluminum hull!

However, a particular copper compound, copper thiocyonate, does not attack aluminum, especially when a primer is applied first. We make sure that appropriate primers and antifouling paints are used for your application.


Here are some facts about antifouling paints:

  • To do its job, the biocide in an antifouling paint is continually released from the paint into the water.

  • Since the biocide continually leaches from the paint, antifouling paints have a limited life span.

  • To compensate for the leaching of the biocide, antifouling paints are designed with mechanisms to keep a fresh supply of biocide exposed to the water.

  • Most antifouling paints (with the exception of copolymer paints) need to be reapplied every Spring because they loose effectiveness over the course of a single year, even if they still look good to the eye.

  • Most antifouling paints (with the exception of copolymer paints) react with the air, and their biocide is rapidly destroyed if the boat is hauled from the water and the bottom is allowed to dry out.

  • Tin-based biocides, which are more effective than copper-based ones, are banned from use on small vessels by environmental regulations.

A neglected bottom.

 Types of Antifouling Paint

A gelcoat bottom with no paint.

Click here to read about the five major types of anti-fouling bottom paints:

- Ablative
- Sloughing
- Modified Epoxy
- Vinyl
- Copolymer

 Call Us

Check with us when your boat's bottom paint needs needs attention. We use quality paints and coatings, and if you have a favorite bottom coating you prefer, we can probably get it for you.

A freshly painted hull.