July 2026 Column Marine Bottom Paints, Part 2 By Capt. John N.Raguso
Preparation is the Key According to Pettit Paint’s Strategic Marketing Manager Matt Anzardo, preparation remains the most critical part of any antifouling project. Even the most advancedcoating will only perform as well as the surface beneath it. Start by evaluating the condition of the existing paint. A coating in good condition will show strong adhesion with minimal flaking, peeling, or excessive build up. One simple field test is to use the serrated edge of a quarter
and draw it across the surface in a wide, controlled arc. If the paint powders, adhesion is typically sound. If it chips or flakes away, further evaluation or removal may be required. If the existing coating is in good condition, it can generally be cleaned, lightly sanded, and recoated. Again, it is important to check a paint compatibility chart prior to application. However, if there is widespread failure or excessive paint thickness, more extensive preparation or removal may be necessary before applying new antifouling. Once the surface condition is confirmed, thorough cleaning is essential. Removing slime, growth and loose material ensures the new coating can properly bond. Any loose paint should be
removed and the remaining surface should be lightly sandedto create the appropriate profile for adhesion. This mechanical bond is critical to achieving a long-lasting finish. The manufacturer’s paint compatibility charts can then guide whether a simple sand and apply process is sufficient or if additional steps, such as sealing with Tie Coat are required. Interlux Bottom Painting Tips Interlux Yacht Paints offers a handy guideline for do-it-yourselfers. The following are some pro guidelines for a successful marine bottom painting experience. 1- Rinse the Surface Rinse the surface with fresh water to remove loose dirt,
growth or any othercontamination. You can also scrub it with a hard sponge. Never clean antifoulingwith solvents as this can damage the surface. High pressure washing removes most of the growth in an effective way. Pay attention on the distance between the surface and the high pressure washer. Some machines have enough power to remove the paint system. Special attention should be paid to clean around the waterline or other areas with visible contamination using an abrasive pad with water.
2- Sanding (painted antifouling in good condition) If the new antifouling is compatible with the existing one, you can normally apply it directly on top of the old one without sanding. However, if the existing antifouling isnot compatible with the new one, you will need to apply a
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