Can you paint over antifouling?

Painting over antifouling is a common question among boat owners, especially when the hull has multiple layers of old coatings. The answer is yes, you can paint over antifouling, but there are important prerequisites and steps you should follow to achieve the best result.

When does painting make sense?

Applying antifouling is useful when:

• The existing layer adheres well and does not show any major detachments or cracks.

• You use the same or a compatible type of antifouling.

• You want to save time and effort instead of removing the old layer completely.

Attention: If the old antifouling is badly damaged or treated with an incompatible product, it is better to remove it completely.

Steps to Successful Repainting

1. Cleaning: Start by thoroughly cleaning the underwater hull to remove dirt, salt residue and loose particles. Use a high-pressure cleaner or special cleaning products.

2. Sanding: Lightly sand the old layer to smooth the surface and ensure better adhesion of the new layer. Use sandpaper with a medium to coarse grit (e.g. 80 to 120).

3. Check primer: If the old coating is badly worn or the primer is exposed, apply a new coat of primer that is compatible with your antifouling.

4. Apply new antifouling:

   • Choose an antifouling that is compatible with the existing layer (e.g. hard antifouling or self-polishing antifouling).

   • Apply 1-2 new coats, making sure to carefully follow the manufacturer's instructions for drying times and coat thickness.

Pay attention to compatibility

Not all antifoulings are compatible with each other. If you are unsure which product can be applied to the existing layer, an adhesion test is recommended:

• Apply a small amount of the new antifouling to an inconspicuous area.

• Allow the layer to dry and check for cracks or peeling.

If problems occur, you must remove the old coating before applying the new product.

When should you remove antifouling?

In the following cases it is better to remove the old layer:

• The coating is cracked, flaking or has come off in places.

• You want to change to a different type of antifouling (e.g. from hard to self-polishing antifouling).

• A thick, uneven layer has built up over the years.

Professional tips for repainting

• Pay attention to weather conditions: only paint at temperatures between 10 and 25 °C and avoid high humidity.

• Use the right tools: Use a foam roller or brush to apply even coats.

• Maintain layer thickness: Layers applied too thickly can impair the effect.

Conclusion: Effort vs. Benefit

Painting over antifouling saves time and resources if existing conditions allow it. With proper preparation and compliance with compatibility rules, you can effectively extend the life of the protection. However, if the old layer is badly damaged or unsuitable, complete removal is the better choice for long-term safe antifouling protection.