In the past, self-etching primer was the go-to coating to apply over bare metal on a car. Metal requires little prep work to apply it, the primer flashes/dries quickly, and it came in 1K Aerosol cans for small jobs. However, in the past 5-10 years you’ve probably been hearing more people talk about epoxy primers and their use as opposed to self-etching primer.
But why use epoxy primer? And what is it, anyway? This non-porous, high-bonding sealer has several advantages when used for certain materials and situations. However, you must be careful about what you apply it to in order to get its full benefits. We decided to give you some insight on where and when epoxy primer works best.
1. Over Bare, Clean Metal – Epoxy primers are amazing at sealing up bare metal and from allowing moisture or corrosion to creep in. Epoxy primer actually seals out the oxygen from the metal, leaving no chance of rust or corrosion forming on the surface like some cheap spray bomb type primers. Etch primer included, epoxy primer is about the only bare metal primer you could leave a vehicle outside in without rust forming back under the primer quickly! Two-part epoxy primers go one step further by including zinc phosphate, which increases its corrosion-inhibiting properties. Simply put, epoxy is the best primer for bare metal, making it excellent for newly fabricated metal parts or ones that have been fully stripped.
2. Mixed Surfaces – Some primers and coatings need the entire surface to be uniform and all the same material. Epoxy primers have excellent adhesion properties and will stick to bare metal, paints, primers and fillers. This means you can hit an area with epoxy primer that’s been sanded down to bare metal, repaired with body filler, and then feathered into the original paint. We suggest blending these areas as well as possible before spraying epoxy primers as they doesn’t have filling/build qualities like a high-build primer and won’t hide imperfections as well. Alternatively, you can apply filler or primer surfacer over the epoxy to fill any minor imperfections and block flat before you paint.
3. Stacking Coatings – Since epoxy primers adhere mechanically, they will grab onto most anything that has a good texture to the surface. For this reason, it works well for stacking if you need to correct an area that you didn’t get perfectly flat and need a little more filler. Just abrade with sandpaper, apply your filler, sand flat and feather the edges. Then you can apply more epoxy primer over top and repeat as needed. This can’t be said for many primers!
4. Use it For a Final Sealer – A cool trick we’ve been doing for the past few years is using our epoxy primer as a final sealer before our base coat. Simply reduce it 50 percent and lay a coat or two down to seal up all of your work and have a nice surface to lay your base coat over top of. The primer has excellent adhesion to most topcoats and will help keep actual paint from flaking or peeling. This is great peace of mind for a lasting paint job.
5. Use it to protect a long-term project – Not all of us have huge, climate controlled shops our project vehicles can sit in until they’re painted. This means you may have to push the project outside overnight or while you do maintenance on the daily driver. Maybe you have a damp shop that flash rusts metal as soon as the temps change? I like to use epoxy primer to seal my work at the end of the day. This way, if I can’t get back to it right away, I won’t come back to a surface-rusted mess! Keep a handful of our 2K AeroSpray™ Epoxy Primer Aerosols on hand for sealing up small areas. They will save you time compared to getting out the spray gun, mixing up primer and then having to clean everything back up!