Waterborne polyurethane coatings effective as corrosion-resistant coating resins

Use of waterborne polyurethane technology is increasing in such areas as construction coatings, automotive coatings, protective coatings and industrial metal coatings. But, can this technology really stand up to these demanding applications? Bayer MaterialScience’s Peter Schmitt, senior technology manager in the Coatings, Adhesives and Specialties group, examined the question in a recent study.
Attendees of Coatings Trends & Technologies 2011, in Illinois in September, had the opportunity to listen first-hand as Schmitt discusses the latest findings about the use of waterborne polyurethane technology in corrosion-resistant coatings. Schmitt presented ‘Waterborne Polyurethane Technology in Corrosion-Resistant Coatings Resins; and began by examining the formulation of waterborne polyurethane technology, as well as the currently available commercial competitive technologies. He discussed the necessary qualities successful corrosion-resistant coatings must possess. Schmitt explained that formulators desire characteristics like corrosion protection for the substrate, adhesion to various types of metal substrates, ease of application and exterior durability when choosing a direct-to-metal coating.
Next, Schmitt presented the advantages of choosing one-component, waterborne coatings for direct-to-metal applications, citing low volatile organic compound (VOC) levels, low odour, ease of field repair and low energy requirements. He compared waterborne polyurethane and waterborne polyacrylate direct-to-metal resins and examined the performance of those resins, as well as blends of waterborne polyurethane and polyacrylate resins, in applications requiring corrosion-resistance.
Straight formula resins and blends were subjected to a variety of tests, including adhesion tests after one day and after seven days, salt fog corrosion-resistance tests and Cleveland condenser humidity-resistance testing. Results of the testing indicated that both the waterborne polyurethane and waterborne polyacrylate resins display excellent humidity resistance. Furthermore, waterborne polyurethane coatings were found to exhibit superior corrosion resistance with a single coat, making them an ideal choice for formulators looking for corrosion-resistant, direct-to-metal coatings.