Epoxy coatings are a mainstay of the protective and marine coatings markets. Used as intermediate coats over inorganic and organic zinc rich primers, or used as direct-to-metal primers in coating systems, epoxy coatings are widely recognized for their versatility and the excellent corrosion resistance they provide.
One drawback to current epoxy coating technology is that it requires separate packaging for the epoxy resins and the amide or amine hardeners because the chemical reaction between these materials causing the applied film to cure to a dry state would also cause the bulk material to gel if packaged together (pot life).
Until now, single-pack epoxy coatings have been based on epoxy-ester resins, which are not as robust as true amine-cured epoxy coatings, or have been based on epoxy resins and latent hardeners, which require a bake cure and therefore are not practical for most protective and marine coating applications. This paper will review the features and benefits of a new epoxy coating technology that allows for true epoxy-amine curing in a single-pack product. Performance versus traditional two-component epoxy products will be compared, and environmental and convenience benefits of single-pack versus two-component packaging will be discussed.
Until around the 1950’s, the vast majority of coatings used for substrate protection were single-component, or “one-pack” coatings. These coatings were supplied in one can in a ready-to-use condition: just open the can and apply. Although many different product types existed, the types of products used for heavy-duty protective applications included coatings based on vinyl-chloride copolymers, acrylic and chlorinated rubber polymers, alkyd resins, and naturally-derived materials such as coal tar and bitumen. Some of these products, notably the solution-vinyl products, provided excellent water and corrosion resistance as well as resistance to many chemicals. However these products were low in solids and had very high solvent content, necessitating up to four or more coats to achieve target dry film thicknesses (1). In addition, the high solvent content has made these products almost obsolete in North America due to Volatile Organic Compounds (VOC) restrictions. Other older single-pack technologies such as alkyd-based coatings are still alive and well, however, like newer technologies based on latex emulsions, they do not provide the same high degree of corrosion resistance as did the high VOC solution-vinyl and chlorinated rubber coatings.