Epoxy or Polyurethane? Which Paint to Use Where

Epoxy and polyurethane are the two most widely used two-component systems in the world of industrial paints. Although they are often thought of as alternatives, in most cases they actually complement each other.

Strengths of epoxy

Epoxy adheres very strongly to metal and concrete, offers excellent resistance to chemicals, oils and abrasion, and can be applied at high film thickness. That makes it ideal as a primer and intermediate coat in corrosion protection systems, and as a topcoat on interior floors.

Its weakness is sunlight. Epoxy surfaces exposed to UV radiation chalk, lose their gloss and may yellow over time. This does not immediately eliminate protection, but it spoils the appearance.

Strengths of polyurethane

Aliphatic polyurethanes in particular retain their color and gloss outdoors for many years. Their flexible film resists cracking under temperature changes, and their abrasion resistance is high. These properties make polyurethane the ideal topcoat for exterior steel structures, tanks, vehicles and outdoor floors.

The two together

The most common and effective solution is to use both systems together: the epoxy primer and intermediate coat protect the substrate against corrosion, while the polyurethane topcoat protects the system against sun and weather. In enclosed areas and floors that never see sunlight, an all-epoxy system is usually sufficient and more economical.

In short: epoxy for interiors and chemical resistance, a polyurethane topcoat for exteriors and long-lasting appearance.