Some surfaces such as plastic will not readily accept paint. The application of an epoxy primer increases the adhesion properties of the surface so the paint will spread properly and stick to the surface. Epoxy primers can also prevent wood tannins from bleeding out and staining the finished top coat of paint.
Epoxy primer acts as a barrier to moisture and helps prevent metals from corroding and wood from rotting. Metals other than galvanized steel need to be coated with a primer if they are to be exposed to rain, groundwater or other types of moisture. Applying epoxy primer to concrete can reduce moisture infiltration and subsequent damage from freeze and thaw cycles.
Epoxy primers increase the strength of materials such as wood and steel. Wood treated with an epoxy primer may be able to withstand exposure to the outdoor weather with less damage or rot than untreated wood. Steel treated with epoxy primer may be able to better withstand impacts, such as automobile crashes.
Epoxy primers may take hours to several days to cure, depending on the weather at the time the primer was applied. This can increase the duration of a home improvement or auto body project. If the epoxy is not fully cured, paint may not properly adhere to the surface of the material.
Cleanup of epoxy primer requires the use of paint thinner or urethane reducer. These chemicals may give off fumes, cause difficulty breathing and skin reactions. They can be toxic if swallowed and can damage any skin they come in contact with. Adequate ventilation is needed when working with epoxy primer and the agents used to clean it.