Primary Marine Epoxy Applications are for components with a high strength/weight ratio and for Epoxy gap filling properties and excellent substrate adhesion
Epoxy Marine Applications: Epoxies are sold in hardware stores, typically as a pack containing separate resin and hardener, which must be mixed immediately before use. They are also sold in boat shops as repair resins for marine applications. Epoxies typically are not used in the outer layer of a boat because they deteriorate by exposure to UV light. They are often used during boat repair and assembly, and then over-coated with conventional or two-part polyurethane paint or marine-varnishes that provide UV protection.
There are two main areas of marine use. Because of the better mechanical properties relative to the more common polyester resins, epoxies are used for commercial manufacture of components where a high strength/weight ratio is required. The second area is that their strength, gap filling properties and excellent adhesion to many materials including timber have created a boom in amateur building projects including aircraft and boats.
Normal gelcoat formulated for use with polyester resins and vinylester resins does not adhere to epoxy surfaces, though epoxy adheres very well if applied to polyester resin surfaces. "Flocoat" that is normally used to coat the interior of polyester fibreglass yachts is also compatible with epoxies.
Polyester thermosets typically use a ratio of at least 10:1 of resin to hardener (or "catalyst"), while epoxy materials typically use a lower ratio of between 5:1 and 1:1. Epoxy materials tend to harden somewhat more gradually, while polyester materials tend to harden quickly.
The classic epoxy reference guide is the Handbook of epoxy resins by Henry Lee and Kris Neville. Originally issued in 1967, it has been reissued repeatedly and still gives an excellent overview of the technology. Some basic tips are given here:www.epoxy.com/install.htm.