A primer is a paint product that can be applied to your boat, underneath the anti-foul and topcoats where appropriate. It works as a 'tie-in' layer that ensures adhesion of the anti-foul. An added benefit of applying a primer is to protect the boat from corrosion and degradation from the surrounding environment. If not used, it can lead to corrosion on steel and aluminium hulls, blistering/osmosis on fibreglass or rot on wooden hulls. Along with protecting the surfaces from the elements, it also gives the final product an enhanced cosmetic finish.
Priming is a must if the material is not water resistant and will be exposed to the elements. As different boats are made out of different materials, there are different types of primers and steps that you must follow to get the best final result. It is possible to tint the primer closer to the desired final topcoat colour to minimize the number of coats/layers that need to be applied to prevent colour bleed through.
Using a primer is highly recommended when painting a wooden boat as wood can be quite porous and will absorb the solvent from the paint, which in turn, dries the paint prematurely. Most paints undergo a chemical reaction during the process of curing. They will depend on water or a solvent being evaporated slowly rather than being absorbed quickly by the underlying material. A layer of primer will help the paint undergo its proper, complete curing cycle. Another reason why it is recommended to use a primer on a wooden boat is it can take several layers of paint to completely cover the wood grain and ensure an even colour all over. Primer also adds a 'waterproofing effect' to the paint used on a wooden boat; If a wooden boat is exposed to moisture, it can warp, develop mildew and/or dry rot. Obviously primers shouldn’t be used for a wood stain treatment that is specifically designed to show the wood grain!
Using a primer on a metal boat is also highly recommended because when bare ferrous metal is exposed to moisture of any kind, it will rust. Some metal primers are available that contain additional materials to protect against corrosion, such as sacrificial zinc.
When priming an aluminium boat, standard paints, even standard epoxy, will tend to peel off an untreated boat. In order to ensure that the primer coat sticks, any portion of the boat that is bare aluminium should be chemically etched to provide a gripping surface for the primer to adhere to. Using a primer will act as an extra insurance against paint flaking off in large bits. There are also special kinds of primers that can be used to chemically convert the rust on the boat in to the solid metal salts. Although the metal may not be the shiny clean metal it once was, it is much better than a weak, porous rust.
Some primers, such as International Paints Primocon©, can be used as a barrier coating to stop the release of banned antifoul compounds, such as TBT, from releasing into the water. By applying the primer over all of the previously antifoulled surface at the required thickness. A new, regulatory approved antifoul can be safely applied over the existing coating without any risk of contamination.
Ultimately, priming is a very beneficial step to take when painting your boat, and should be part of your process to ensure you get the most out of the antifoul layer. Primers come in a variety of types to serve a variety of functions, so it is important that you select the right primer for your boat, whether single pack, underwater, two pack or aluminium.
Here at Booker Bay Marine, we sell International Primocon©, Altex Mutlipurpose primer undercoat©, Altex Primashield©, Altex Epoxy Primer mixed pack© and Jotun Penguard mixed pack© as well as having access to the full product ranges of the aforementioned brands.
Multipurpose primer© can be used on prepared steel, lead, wood, and GRP. This primer is a single pack that can be used as both above and below the waterline. Multipurpose primer© can be used on prepared steel, lead, wood, and GRP. This primer is a single pack that can be used as both above and below the waterline. Multipurpose primer© can be used on prepared steel, lead, wood, and GRP. This primer is a single pack that can be used as both above and below the waterline. Primashield© can be used on mild steel, corten steel hulls & keels, timber hulls, and exposed fibreglass/gelcoat/GRP. This is also used as a single pack below the waterline primer. Primocon© is suitable for all surfaces whether it be steel, wood, aluminium, cast iron keels and lead keels. This is used as a single pack below the waterline. Altex Epoxy Primer mixed pack© is suitable for steel, alloy, GRP, and wooden substrates. Altex Epoxy primer is best used as a below the waterline.