Aside from its adhesive and filling characteristics, one of the many amazing qualities of epoxy resin is its ability to seal and provide a watertight (and anti-corrosive) layer of protection. In fact, it's one of the only materials that can do this. While polyurethane coatings can be applied to metal or plastic substrates and then sealed with a topcoat, they are not as resistant to corrosion as an epoxy coating. Resin can be applied to a variety of surfaces - including wood, metal, and even ceramics - and cured into a protective film. The type of resin used will determine how it cures and what it can be used to protect against. For example, epoxies are available in liquid form and can be painted onto a substrate before curing, while silicones must be sprayed onto a surface and will not cure until exposed to air. Once it has cured, resin is very hard to remove from most surfaces it contacts. This includes paint, fiberglass, plaster, concrete, etc. However, there are chemicals available that can break down some types of resin, such as those used for sealing furniture. Otherwise, you would need to physically scrape off the damaged portion of the material. It is important to realize that although resin can be waterproof, it can't prevent all damage caused by water.