News from Sherwin-Williams Protective & Marine Coatings

When engineers from Short Elliot and Hendrickson, Inc., of St. Paul, Minn., were asked to specify a coating for a bridge in International Falls, Minn., one of their primary concerns was selecting a coating that could be applied in cold temperatures and withstand harsh weather over time. They also needed a coating that could speed job turnaround. After all, as one of the coldest states in the continental U.S., their painting season is short. Owned by Minnesota, Dakota, & Western Railway Company (MDW) and the International Bridge & Terminal Company, the bridge serves as an important crossing on the U.S. - Canada border. More than one million trucks and cars use the bridge every year. The original through-truss steel bridge was constructed in 1908. A concrete bridge to accommodate increased traffic was added next to the bridge in 1979. Spanning approximately 940 feet over the Rainy River, the bridge’s primary purpose is to convey trains and process piping that runs from one section of a paper mill to another located across the river in Fort Francis, Ontario. Finding the right coating for the job was no small task. Known as the “Nation’s Icebox,” International Falls has an average temperature of 36.4°F. In the ‘60s, the city’s chilly climate inspired the name “Frostbite Falls” used in the “The Rocky and Bullwinkle Show,” a popular television cartoon. After completion of a bridge inspection and coatings evaluation process, the engineering firm recommended a coating system comprised of Corothane® I Galvapac Zinc Primer and Fast Clad® Urethane from Sherwin-Williams. The system, which incorporates new resin technology, was selected for its ability to provide long-lasting protection against corrosion and abrasion. An additional benefit is that it is a two-coat, not a three-coat system, allowing for faster turnaround. The use of the two-coat system has a proven track record in other parts of the country as well. The Northeast Protective Coatings Committee (NEPCOAT) has tested and recently approved it for new and 100 percent bare existing steel for bridges. The coatings comprise the only two-coat system approved for such projects. Nine states including Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York Pennsylvania, Rhode Island and Vermont belong to NEPCOAT. Corothane I Galvapac Zinc Primer is a moisture curing urethane, zinc rich primer. It offers excellent bonding over blast or tool cleaned steel surfaces. The primer can be applied at three to four mils dry film thickness (DTF). Fast Clad Urethane, the topcoat, features new polyaspartic resin technology that provides excellent application features like high volume solids, a tightly cross-linked film with no outgassing and sharp edge retention, and excellent color and gloss retention. The raw material resins for the paint were supplied by Bayer MaterialScience, LLC. For the International Falls project, the coating was applied at six to nine mils DTF. The primer and topcoat are VOC compliant, can be applied at temperatures as low as 20°F, and dry fast, allowing painters to work quickly. Painting crews also save time because the system requires only two coats. Doni Riddle, vice president industrial and marine marketing, Sherwin-Williams, notes that the system provides the same long-term performance and protection as conventional, three-coat systems. The coatings are applied with conventional spray equipment. “The two-coat system allows a bridge to be painted in two-thirds the time it would normally take, with a cost savings of approximately 22 percent,” he says. Photo Caption: A new two-coat system featuring Corothane I Galvapac Zinc Primer and Fast Clad Urethane from Sherwin-Williams was used on the bridge at International Falls, Minn. The system can be used in temperatures as low as 20°F, dries fast and provides the same long-term performance and protection as conventional three-coat systems.