How to Apply Epoxy Primer

Posted: May 15, 2014 By: Louis Beaudreau

Epoxy primer serves a wide range of automotive needs, providing quality resistance to corrosion, fast build, exceptional color holdout and strong adhesion to bare metal substrates. Epoxy primer is specifically ideal for using after sand or media blasting projects due to its filling qualities. Below, we take a look at how to properly apply an epoxy primer to the body of your vehicle.

Step #1: Surface Preparation

First, if you are using epoxy primer on bare metal surfaces, it is important that all existing finish and corrosion has been properly blasted or stripped off. To prepare a bare metal surface for this primer, clean it with a wax and grease remover. This will ensure that all road grime, dirt, grease and other surface contaminants are removed. It is important that the metal surface is slightly abrasive so that the primer coat will be more adhesive. When you are applying epoxy primer over already existing finishes, use these same steps above, and make sure to abrade the surface with 320 to 400 grit sandpaper. Always be sure to clean the metal surface with the wax and grease remover again after abrading it.

To prepare the epoxy primer, shake or stir the primer, and thoroughly mix one part primer with one part catalyst. To reduce any film buildup, this one to one ratio can also be cut with a urethane-grade reducer or comparable solvent solution. This can also improve the overall flow of the primer mix. Be aware that epoxy primer can begin to gel after only 90 minutes in a 70 degree environment. If you are using an HVLP spray gun to coat your primer, make sure the fluid tip is between 1.4 and 1.8 mm and the spray pressure is between 25 and 30 psi. If you are using a conventional gravity gun to coat your primer, make sure the fluid tip is between 1.4 and 1.6 mm and the spray pressure is between 45 and 55 psi. If you are using a conventional siphon to coat your primer, make sure the fluid tip is between 1.6 and 1.8 mm and the spray pressure is between 45 and 55 psi. Once you have the spray gun and primer mix prepared, it is time to apply it to your metal surface.

Step #2: Primer Application

The epoxy primer should be applied in medium wet coats, allowing a half an hour between each coat at around 70 degrees. One to two coats will render a one millimeter dry film thickness, which is typically enough to be completely effective. Make sure to evenly spray each coat completely across the bare metal surface. If your spray gun is spraying unevenly, it needs to be properly cleaned. Epoxy primer can be topcoated after about 30 minutes (45 minutes to an hour if more than two coats were applied), or even up to five days after the last coat. If you are waiting more than a couple days, the surface should be lightly sanded again prior to topcoat application. Once you’ve applied all of the coats, the surface can be wet sanded after a single day, but it is best to wait two to three days before dry sanding.

As always, make sure you are wearing the proper safety equipment (goggles/face mask and gloves) while performing this task. Also, be sure to seal each of your solution containers and properly clean your spray gun immediately after each use. That way, your equipment will be ready to use the next time you need to apply an epoxy primer.

To learn more about epoxy primer and for more DIY car tutorials, be sure to visit

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