Types of Anti-foul Paint

Anti-fouling generally falls into two types: ablative or self-polishing (soft), and nonablative (hard) coatings.

Ablative coatings require no maintenance during their lifetime. As the boat is used the action of the water brushes off any attached organisms, taking a small amount of paint with them. Thus a fresh active surface is regularly exposed, and the paint layer wears down over time.

When it is due for renewal there is less to be scraped or sanded off before applying a new coat. However, these products are soft and easily damaged, and are not suitable for high-speed boats or vessels stored on moorings that dry out between tides.

The hard type of coatings does not wear off, and retains the surface finish. These are resistant to abrasion and rubbing. However, the active ingredient on the surface gradually loses its effectiveness and should therefore to be manually scrubbed or lightly sanded regularly to expose a new active surface. When due for renewal the original coating needs to be fully removed (sanded or scraped off) before a new coating is applied.

There are also some specialist thin film coatings for performance boats, which require specialist application and are mostly outside the realm of DIY application.

The active ingredient in anti-foul products is usually based on some form of copper compound, since copper is toxic to most marine organisms. However electrolytic action with the copper will cause an aluminium hull to corrode like an anode, so special noncopper-based compounds are needed for aluminium boats.