An epoxy-coated motor boat out on the water

To complement the launch of our UltraClear Marine Epoxy Resin, we've written a guide explaining what it's for and how to use it. We'll also address how it compares to similar alternatives.

What is marine epoxy used for?

Marine epoxy is a medium viscosity epoxy resin designed to withstand harsh aquatic environments. Our marine epoxy resin cures in thin layers using special hardeners. Its primary purpose is to protect surfaces that are consistently exposed to the unique environmental elements of lakes, seas, and the ocean.

When used with an appropriate hardener, marine epoxy resin cures with a translucent finish and may have a subtle yellow-orange hue. This is generally not of concern, as the epoxy itself is often painted over or fully concealed in other ways later.

Marine epoxy is frequently used to protect the hulls of watercrafts such as kayaks, canoes, skiffs, etc., as well as larger boats. It is also applied to related accessories and equipment that one might use on lakes, rivers, seas, or oceans.

To prepare most boats for the water, epoxy barrier coats are applied to the hull surface (usually made of fiberglass). These long-lasting coats are added before any bottom paint and will provide the exceptional moisture resistance needed to keep the boat healthy for many years. With proper care, an epoxy coated vessel can endure wide temperature shifts and high degrees of salinity.

Marine epoxy is also used for repairing hull damage and for fairing hulls to make a damaged surface smooth again.

Marine grade epoxy resin is also a better option for the formation of composite materials like fiberglass, which is a very common choice for boat construction and related components. Choosing epoxy resin over similar resins like polyester will result in a more durable composite material.

Two people on separate marine epoxy-coated kayaks.

Epoxy resin vs polyester resin:

Epoxy resin is often compared to polyester resin, since they both share similar purposes. Generally, if you can choose from either of them, epoxy will be the better option. Polyester's primary advantage is that it is cheaper, but in turn it is less protective and less effective than epoxy.

Here are some of the advantages of marine epoxy over polyester resin.

  • Marine epoxy has better moisture resistance. This is obviously a big deal for watercraft, which are in constant contact with water.
  • Marine epoxy has a higher flexural strength rating. It can handle greater force without bending once cured.
  • Marine epoxy can be applied in thinner layers without experiencing curing problems. Polyester can be difficult to work with at the same level.
  • Marine epoxy can be used to repair a polyester base. While polyester resin struggles to bond with cured epoxy, marine epoxy resin can safely bond with cured polyester. This is because cured polyester is not as smooth at a microscopic level as epoxy.
  • Marine epoxy resin is more resilient. Unlike polyester, it won't easily shrink or warp under higher temperatures as it cures.

Note: Cured epoxy doesn't properly support a polyester gelcoat finish. If you decide to apply a gelcoat as your final finish, use an epoxy gelcoat.

What surface materials can marine epoxy bond with?

Most watercraft hull materials are fine with marine epoxy. These include very common options like:

  • Fiberglass
  • Wood
  • Metal (e.g., steel, aluminum)
  • Other typical composite materials

Marine epoxy resins uses special hardeners

Marine epoxy resin is generally used with one of two types of hardener: a fast hardener or a slow hardener. UltraClear offers high quality variants of both.

Our UltraClear Epoxy Fast Hardener has a shorter working time of 12 minutes and begins to cure quickly when in the recommended temperature range of 60°F - 70°F. It will fully settle about 6 hours after mixing and tends to be slightly less translucent than slow hardeners.

On the other hand, our UltraClear Epoxy Slow Hardener has a longer working time of 30 minutes before the curing reaches an unworkable point. It can cure at a higher temperature of 80°F or above. It is also slightly more translucent as a finish, though this usually won't matter for the kinds of projects it's designed for.

Wooden boats with a marine epoxy coating

Have questions about marine epoxy? Want planning advice? Contact us!

At UltraClear Epoxy, we value high quality customer service. If you have any questions about our marine grade epoxy resin, or if you would like some assistance in planning an epoxy project or gathering the necessary supplies, you can contact us via email or phone. You can even text chat online with one of our epoxy experts by clicking the help button at the bottom right of your screen.

Epoxy basicsMarine epoxy

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