Enhancing the UV Durability of Epoxy Coatings: Waterborne Acrylic-Epoxy Hybrid Coatings for Steel

Abstract

abstract Due to their excellent performance properties, epoxy coatings are commonly used over metal and concrete substrates in applications where corrosion protection and chemical/solvent resistance are key requirements. One weakness of these epoxy coatings is their poor UV durability. Epoxy coatings typically have poor gloss and color retention as well as poor resistance to chalking on exterior exposure. Many epoxy coatings also contain solvents which contribute to high volatile organic compound (VOC) levels. Waterborne epoxy coatings can often be formulated to low VOC, but exterior durability still remains a challenge. Combining excellent corrosion protection and chemical/solvent resistance with exterior durability and low VOC in a coating based on epoxy chemistry is not an easy task. This paper will describe a new two-component waterborne acrylic-epoxy technology that facilitates direct-to-metal (DTM) coatings with this important balance of properties. The system has versatility in that the acrylic-epoxy hybrid polymers can be cured with either traditional waterborne amine hardeners or with acid-functional acrylic hardeners. Performance of the waterborne acrylic-epoxy hybrid technology in single-coat gloss DTM coatings and anticorrosive primers will be described, along with comparisons to traditional waterborne and solventborne epoxy coatings.