A research team at the University of Nevada, Reno has developed an environmentally friendly coating for aluminum to replace chromate coatings used in aerospace applications. The team presented its research at the international Pacific Rim Meeting on Electrochemical and Solid-State Science in Hawaii.

“It was well-received at the conference,” says Dev Chidambaram, lead scientist and assistant professor of materials science and engineering at the school. “There is no question that this will be able to replace the chromate-based coating. Even though the coating formulation is yet to be optimized, the coating has shown exceptional performance.”

The search for a suitable replacement has been elusive primarily due to one main characteristic of the coating referred to as “self-healing”—the ability of the coating to heal itself after being damaged or scratched.

When it is scratched, coating components from nearby sites migrate to the damaged region and re-protect the underlying alloy, Chidambaram says. He says the formulation performs comparably to the chromate formula in its ability to self-heal, which is important to the defense and aerospace industry.

“The coating can be applied to all aluminum products,” Chidambaram says. “The new formula creates an environmentally benign, molybdate-based coating that provides corrosion protection to aluminum used for aircraft and spacecraft. These coatings, when damaged, will re-heal themselves.”

The University of Nevada, Reno team developed and tested more than 300 coatings before arriving at this formulation. It 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. In addition, using electrochemical testing, the team showed that the coating re-protected itself via self-healing upon scratch testing.

“This has taken 14 years of work, continuing on work I did at the State University of New York at Stony Brook and the Brookhaven National Laboratory,” says Chidambaram. As director of the university’s Materials and Electrochemical Research Laboratory (MER Lab), he has obtained nearly $3 million in externally funded research grants in the past three years, and directs eight doctoral students and one postdoctoral associate.