Scientists in Singapore have come up with a metal coating that’s based on polymers. The coating can fix itself after it gets scratched, which helps to protect the metal underneath from rust. Some studies have estimated that the annual cost of corrosion is roughly 1-5% of each nation’s gross domestic product in the U.S., Japan, China, and Europe.
There have been similar examples of coatings like this, but, as Heather Montgomery points out in a Chemistry World article, this particular one doesn’t need a catalyst and works at room temperature. The research on the new coating was published in the Journal of Materials Chemistry.
Mingxing Huang and Jinglei Yang of Nanyang Technological University made the coating by capturing the highly reactive compound hexamethylene diisocyanate (HDI) inside polyurethane, which is a polymer, in microcapsules. Next, they dispersed the microcapsules into an epoxy resin and slapped on the coating onto a steel surface.
When the researchers scratched the coating with a razor blade, the microcapsules burst open to release Â HDI. The chemical is highly reactive with water so it reacted with moisture to make polyurea, which then sealed the damaged region. The researchers carried out a control experiment with just the epoxy resin and determined that a similar sealing process did not take place.
However, both the authors and materials expert Fred Wudl of the University of California Los Angeles, US, agree that more work is needed before the system is ready for real applications. ‘The vesicle membranes are too permeable to moisture and the shelf life, particularly in a humid environment, would be too low for immediate applications, particularly the anticorrosive application the authors have in mind,’ says Wudl.
The duo of researchers are currently improving the polymeric coating by analzying how the microcapsule concentration and coating thickness affects the kinetics of the healing process of the scratched surface.
Source: “Rust busting self-healing materials,” Chemistry World, 06/30/11
Source: “Coating Said to Heal Without Catalyst,” PaintSquare, 07/01/11
Image by J from the UK, used under its Creative Commons license.
Rajendrani "Raj" Mukhopadhyay is a science writer and editor who contributes news stories and feature articles on scientific advances to a variety of magazines. Raj holds Ph.D. in biophysics from Johns Hopkins University.