Paint coatings for marine or pleasure boat use are usually either single pack or two pack materials. Single pack products can be used as they are and dry by reacting with oxygen in the air. Two pack products cure by a chemical reaction that begins once you mix the Part A, or the Base, with what is known as either the hardener, converter, curing agent or Part B.
In both types of systems there are three broad groups of products known as primers, undercoats and topcoats. Primers seal substrates and provide various levels of water and corrosion resistance. They also act as a tie-coat so the undercoats and then the topcoat can adhere to each other and the substrate. In some cases undercoats are not required.
Pro tip: Remember that you can apply single pack products over two pack, but you cannot apply two pack products over single packs. The strong solvents in the two pack will lead to serious defects in the system making it unusable.
There are numerous reasons for and against for both single and two pack systems, but there are three important factors that might influence your choice of product.
You could choose a hybrid system that offers some of the benefits of both single and two pack systems. In other words, use a two pack primer with all the benefits that brings with it and then revert to the simple and easy to use single pack undercoat and topcoat system. Such a system is widely used below the waterline for permanently immersed vessels where a two pack epoxy primer will be applied. This is then followed by antifouling paint that’s usually a single pack product.
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