October 23, 2012
New Non-Toxic Coating Makes Aluminum Corrosion-Free
[WATCH VIDEO: Formation of Corrosion Protective Molybdate Coating]
redOrbit Staff & Wire Reports - Your Universe OnlineResearchers have developed a new, non-toxic coating for aluminum that can replace the carcinogenic chromate coatings used for more than half a century to protect aluminum from corrosion.
"There is no question that this will be able to replace the chromate-based coating,” said lead researcher Dev Chidambaram, assistant professor of materials science and engineering at the University of Nevada, Reno. “The coating has shown exceptional performance.”
Attempts to replace chromate coatings with environmentally friendly coatings have been underway for decades.
Although the use of chromates for consumer and automotive applications has been banned, it is still in use by the defense and aerospace industries under various exemptions. These exemptions are due, primarily, to the unavailability of suitable replacements along with the high human and financial costs of failure from corrosion.
But the search for a suitable replacement has been elusive, primarily due to the “self-healing” characteristic of the coating, which allows it to heal itself after being damaged or scratched. When scratched, the coating components from nearby sites migrate to the damaged region and re-protect the underlying alloy.
But Chidambaram's formulation performs comparably to the chromate formula in its ability for self-healing, and can be applied to all aluminum products. It also offers an environmentally-safe molybdate-based coating that provides adequate corrosion protection to aluminum.
The researchers developed and tested more than 300 coatings before arriving at their ultimate formulation. They used a complimentary suite of advanced surface analytical techniques such as Raman microspectroscopy, Fourier transform infrared spectroscopy, energy dispersive spectroscopy, secondary ion mass spectroscopy and X-ray photoelectron spectroscopy to conclusively prove the presence of molybdate in the scratched region.
Next, they used electrochemical testing to demonstrate that the coating re-protected itself via self-healing upon scratch test.
The team is still working to optimize the coating formulation for even greater protection.
The researchers presented their work last week at the international Pacific Rim Meeting on Electrochemical and Solid-State Science in Hawaii.