How do I choose a finish?

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. 

More details to consider
 

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.

1. Health and safety is an important factor when using paint, and two pack products contain stronger solvents and more reactive chemicals that pose a higher health risk than the single pack. Wearing the correct safety gear mitigates that, but if you don’t have good ventilation or a suitable place to use two pack, then single pack is the better choice.
2. Because of their chemistry and the ingredients used to make them, two pack paints will be more expensive. Also, remember that for a two pack gloss finish, you would need to use two pack primers and undercoats. As equipment is not so easy to clean and reuse, the cost of the paint plus consumables will be higher.
3. Two pack systems do offer the highest levels of water resistance, toughness, corrosion resistance and durability, so they do make an excellent choice for a paint system anywhere on a vessel.
    

Another option.
 

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.