As boat owners, we have all seen boats in the yard being primed. Perhaps the entire hull, or just patches here and there. But why? Perhaps you are antifouling your own boat and wondering if you need to prime anything? Let's look into this in more detail!
When to prime?
There are a couple of reasons you may choose to prime before re-antifouling. The first, you have just bought the boat, have no idea what antifouling the previous owner has used and you are worried about adhesion. This is when you may consider priming the entire hull.
The second, you have some antifoul missing from the hull or metal parts. This is when you may consider patch priming the bare spots.
The photo below shows some white areas (on a white hull) that have been exposed after some extensive machine sanding on some rough antifoul. These white areas may be gelcoat OR existing epoxy primer that has been applied as a barrier coat to prevent moisture penetrating the gelcoat and causing osmosis. The white areas need to be primed before re-antifouling.
This boat has been poorly prepared and re-antifouled in the past. GC Boat Antifouling will not cut corners on the preparation of your boats hull!
Why Prime before re-antifouling?
Sticking with the same examples, priming the entire hull if the existing antifoul is unknown, ensures adhesion of the new antifouling system to the existing. Given the products on the market today, it is likely that you wouldn't have an issue with adhesion between new and existing antifouls if the the existing antifoul is well prepared, however a primer is a safe bet.
Patch priming exposed metal parts such as trim tabs or through hull fittings not only ensures adhesion, but creates a barrier coat over the metal to minimise corrosion. If you find your metal fittings below the waterline are missing antifoul each time you haul out, then you may need to consult a specialist to inspect your bonding system and anodes. 'Blasting' of antifoul coatings from metal parts is not normal and is generally a symptom of a larger problem that can result in corrosion of underwater metals and extensive repairs in the future.
Patch priming exposed gelcoat or epoxy barrier coat is essential to ensure that the gelcoat is protected from absorbing moisture.
How to prime and what to use?
In most cases, we recommend using the primer recommended by the brand of antifouling that will be applied. For Jotun antifoul, the primer would be Vinyguard 88. For International antifoul, the primer would be Primocon. Both of these primers are a single pack primer that can be applied over existing single pack antifoul.
Bare gelcoat or metal surfaces could be primed with a 2 pack epoxy primer to provide greater corrosion and moisture protection however care must be taken to minimise the application of 2 pack paints over existing single pack antifouls as the solvents may soften the antifoul and cause future coating failures. For this reason, we recommend a single stage primer applied inline with the manufacturers documentation.
Boats live in a harsh environment so be vigilant, and haul your boat out of the water every 12 months (minimum) as part of a preventative maintenance program.
If you have a boat on the Gold Coast and want your antifouling, Propspeed and Anodes done the right way, why not give us a try? You won't be disappointed.
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