Blue bar, spraying gray on red panel and pouring blue paint

December 2014

With today’s direct to metal (DTM) primer technology you most likely won’t need an etch primer to achieve the coating performance you desire. A single primer can give you the adhesion and corrosion protection that previously was only achieved in a two product, two step process. With that in mind, it is critical to choose the DTM primer that best fits your needs. Although very similar, epoxy and urethane primers each have a few distinct attributes that you need to understand before making your selection.

 

The Similarities

  • Both provide excellent adhesion to multiple metals and plastics.
  • Both can be solvent or water based.
  • Both come in various VOCs and colors.
  • Both can act as a sealer or a surfacer (we will talk about the differences between those two later).

 

The Differences

Epoxy primers typically provide slightly better long term corrosion protection by creating a harder and more chemically resistant coating. Epoxies also provide excellent water resistance and minimal shrinkage.

 

Urethane primers have the advantage of speed. They tend to have better topcoat compatibility which allows your topcoat to be applied faster over the primer. You will see less topcoat dieback, which is a loss of gloss when fully cured, in a urethane primer versus an epoxy.

 

Urethane primers also hold up against UV rays much longer than epoxies. Epoxy primers will fade and yellow much quicker when exposed to UV rays because epoxy chemistry is broken down faster by high energy UV rays.

 

When selecting the primer that best fits your painting process and end-use environment, keep all of the factors listed above in mind. Although the primer is not often seen, its protection and qualities are critical to the longevity and color of your coating.

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