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Epoxy primer is a thermosetting polymer often used to prepare bare metal for painting, such as for cars or boats. There are a number of factors to consider when choosing an epoxy primer for your project: application type, project-specific usage and the supplies and labor required to prepare the surface. There are so many types of epoxy primers, so it is important to have a plan for your project ahead of time.
Epoxy primer comes in two different forms: in an aerosol can or in a larger bottle or bucket. The primer in a can is usually meant for smaller projects, such as priming a chair and not a car, and it often uses a one-step application for smaller projects. Epoxy primer when sold in larger quantities usually requires the purchase of two parts, the primer and a converter, which are then mixed together before application. Although the greater amount offers more flexibility, you must mix the amount needed for the project before each application, because mixed primer cannot be stored for extended periods of time.
Usage of the primer in your project will be the primary consideration, because not every paint type will work with every primer. Some epoxy primers can be used only as base coats, and others are suitable for use as a protective coating on top as well. Many come in multiple colors, depending on what color the paint on top will be. Also, although most non-aerosol primers are suitable for both roller/brush and spray application, some will need reducing before they can be used with a spray system. Other things that might not be vital to the outcome of the project but are useful to consider include curing time and whether a primer is lead-free.
If you are planning to prime an object that will spend a lot of time in water, you might wish to choose an epoxy primer designed for marine use. Although these are frequently more expensive, they offer the increased robustness required for that environment, and a standard epoxy primer might not. Marine epoxy primers are more than just waterproof paint — they also have to resist oil and salt corrosion.
Another important factor in choosing an epoxy primer is what other supplies you have on hand or are willing to buy in order to prepare the surface for priming. Some epoxy primers will require the use of a chemical self-etching primer beforehand to improve adhesion, and others will work fine with manual abrasion such as sandblasting. The method to which you have access might determine the type of epoxy primer that will be best.
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