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Graphene Coating: Non-toxic Rust Buster

Friday, May 18, 2012

More items for Coating Materials

Scientists have a new secret weapon in their quest for a steel coating that effectively fights corrosion without using toxic compounds.

It’s graphene, which is fast showing its worth in a wide range of leading-edge coatings technologies.

Photos: University at Buffalo

A graphene-based coating under development at the University at Buffalo keeps a piece of steel rust-free (foreground), in stark comparison with a rusted sheet of steel (background).

University at Buffalo researchers have announced “significant progress” on creating a graphene-based coating that keeps rust at bay longer than conventional protective coatings that contain toxic hexavalent chromium.

Battling Brine

In the scientists’ first experiments, pieces of steel coated with the high-tech varnish remained rust-free for only a few days when immersed continuously in saltwater, an environment that accelerates corrosion.

But by adjusting the concentration and dispersion of graphene within the composite, the researchers increased to about a month the amount of time the treated steel can survive in brine.

Because brine is an extremely harsh environment, the coated steel's survival time in the real world would be many times longer, the team says.

The material's hydrophobic and conductive properties may help prevent corrosion, repelling water and stunting the electro-chemical reactions that corrode metal, said Assistant Professor Sarbajit Banerjee, PhD, a materials chemist.

Banerjee is leading the research with doctoral student Robert Dennis, who discusses the project in a video interview.

Patent Application, Support

The team’s next step is to use a $50,000 grant from the New York State Pollution Prevention Institute to enhance the coating’s durability and finish quality, the university reports.

“The development of an environmentally friendly alternative to hexavalent chromium would truly revolutionize this sector,” said Anahita Williamson, PhD, the institute’s director.

Three solutions for rust-proofing steel contain varying amounts of graphene. The research could produce less toxic, more effective protective coatings.

“The metals plating industry identified this as a high-priority research project, and NYSP2I is excited to support UB researchers in their efforts to develop solutions.”

Global steel producer Tata Steel is also supporting the work, as the scientists test larger and larger samples, Banerjee said.

The university has applied for a patent on the coating. Tata Steel would also share in those rights.

“UB has been one of our choices for cutting-edge coatings technology development on steel substrate," said Debashish Bhattacharjee, PhD, Tata Steel's group director for Research, Development and Technology.

‘A Chance to Reinvent’

Bringing the coating to the market could benefit public health and save jobs, the researchers say.

“Our product can be made to work with the existing hardware of many factories that specialize in chrome electroplating, including job shops in Western New York that grew around Bethlehem Steel,” Banerjee said.

“This could give factories a chance to reinvent themselves in a healthy way in a regulatory environment that is growing increasingly harsh when it comes to chromium pollution."

Graphene Coatings

Graphene, the thinnest and strongest material known, has flexed its muscle in coatings research before.

The focus of the 2010 Nobel Prize for Physics, graphene consists of a single layer of carbon atoms linked in a honeycomb-like arrangement. The flake of carbon can conduct heat, electricity and copper.

“Graphene is stronger and stiffer than diamond, yet can be stretched by a quarter of its length, like rubber. Its surface area is the largest known for its weight,” said Andre Geim, one of two Nobel Prize winners recognized for their graphene research.

In the coatings world, graphene was recently crowned the key ingredient in the thinnest coating ever for protecting metals from corrosion. It has also shown promise as a super-slick antifouling and has even demonstrated potential to harvest energy from flowing water.