Chromate-Free Nanoparticle Corrosion Inhibitors for Steel

The corrosion of steel has widespread economic and environmental effects; the annual cost of corrosion exceeds $275 billion. Approximately 40 percent of U.S. steel production is dedicated to replacing corroded metal parts and consumer goods. Corrosion also has a significant impact on the environment. Structures such as storage tanks, pipelines, ships, railcars, and tanker trucks, which store and/or transport hazardous materials, frequently are damaged by corrosion and leak their contents into the environment. For example, corrosion is the leading cause of leaking storage tanks, which in turn threatens public health and leads to billions of dollars in direct and indirect environmental costs. Chromate-load organic coatings are the most effective method of preventing corrosion of metals such as steel. Unfortunately, hexavalent chromate corrosion inhibitors produce their own environmental problems, and their toxic properties are well documented. The use of chromate corrosion-inhibiting spray-on coatings produces chromate containing leachates and inhalable chromate-tainted dusts. Furthermore, the removal of chromate corrosion-inhibiting coatings by chemical or mechanical means also generates hazardous chromated waste. Because hexavalent chromates are known carcinogens, their use and disposal are strictly regulated. In fact, in much of the developed world, their use and disposal are being banned outright. Better technologies are clearly of economic, public health, and environmental importance. In this Phase I research project, TDA Research, Inc., proposes to develop a chromate-free corrosion-inhibiting nanoparticle additive for steel. These nanoparticles will have effective organic corrosion inhibitors anchored to the surface that are triggered to release by the corrosion process. While anchored, the corrosion inhibitors are nonleachable, but when released they migrate to arrest corrosion at the metal surface. The use of the triggered release from the nanoparticle platform reduces leaching of the corrosion inhibitor out of the coating and into the environment, and increases the effectiveness and life cycle of the coating. There is a large market for protective corrosion-inhibiting coatings, roughly $6.7 billion per year in the United States. A chromate-free corrosion coating for steel could be used for a range of applications, including automotive, aerospace, bridges, buildings, and military.