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Bottom Paint Types

 Types of Antifouling Paint

There are five main categories of antifouling paint designed to release their biocide at a controlled rate:

  1. Ablative antifouling paints allow their surface to be constantly worn off a tiny bit at a time to keep a fresh layer of paint and biocide exposed to the water.

    • This type of paint uses the vessel's motion through the water to wear off the outer surface.

    • If the boat sits in port for a long time, ablation won't occur and the outer surface won't be renewed.

    • High boat speeds accelerate ablation.

  2. Sloughing antifouling paints also allow their surface to wear away.

    • The paint is lost in visible flakes instead of invisibly as with ablative paints.

    • Sloughing paints are cheaper than ablative paints.

  3. Modified epoxy antifouling paints are not ablative.

    • They are called "modified" because they are a one-part epoxy paint.

    • They make a hard, tough coating that does not wear away.

    • The copper particles in the paint slowly dissolve into the water. The more they dissolve, the deeper into the paint the water can penetrate to reach more copper particles until the copper is all consumed.

    • They are compatible for use over most pre-existing coatings.

    • They are difficult to remove.

    • If a new layer of paint added annually without first removing the old paint, eventually the accumulated paint will become so thick it will crack and peel off.

  4. Vinyl antifouling paints are also not ablative.

    • They contain potent solvents that can attack and bubble pre-existing coatings if not used correctly.

    • They work like the epoxy paints in that they do not wear away, but the biocide is still designed to leach out.

    • They produce a hard finish that is the smoothest of the antifouling paints, and the best for high speeds.

  5. Copolymer antifouling paints are a newer development that binds the biocide to the pigment within an ablative binder.

    • They are multi-year paints that remain effective as long as they look good to the eye. This is in contrast to other types of antifouling paint which become ineffective although they may still look fine.

    • They retain their antifouling effectiveness even after being hauled out of the water for long periods. However, they need to be reactivated by scrubbing with a stiff brush or by light pressure-washing. This distinguishes them from other antifouling paints.

    • They are a type of ablative paint that wears thin with time and abrasion.

    • Their surface gradually dissolves in the water even when the boat is stationary, so they remain effective when the boat is in port for long periods.

    • They do not withstand scrubbing well because it rapidly wears the paint layer thin.

    • They are easy to maintain. Since repainting does not have to be done annually and both the paint and biocide are removed equally by ablation, thick accumulations of old paint are avoided.